In fish ponds, it is essential to have good quality water. Without such water, fish in the fish pond will die.

This is especially so with koi fish.

The main cause of water deterioration in fish ponds is the result of the fish in the fish pond eating and producing waste products such as urine and excreta. If a fish pond has no filtration system and a fish stock level which is too high for natural plant life to effect a degree of filtration, then ammonia produced from the fish waste matter will rise to such an extent that it will cause the death of the fish in the pond. So-called biological filters are employed to filter the water such that the ammonia is naturally converted into beneficial compounds and such that the oxygen level in the water is maintained at a level which will support fish life in the pond.

A major problem with the biological filters is that they tend to become blocked. The filter medium is a dense substance which is easily clogged by fish excreta and dirt.

A clogged biological filter does not perform properly because the supply of oxygen to the clogged areas of the biological filter becomes cut off.

Fish ponds may have pump fed filtration systems or gravity fed filtration systems. Pump fed filtration systems utilise a pump. If the pump is a submersible pump then the pump is located in the pond. If the pump is an external pump then the pump is usually located beside the pond. A pond owner has the option of sucking water from the bottom of the pond or from a mid-water area between the top of the pond and the bottom of the pond. If the water is sucked from the mid-water area, there will be an accumulation of fish excreta and debris on the bottom of the pond. This fish excreta and debris is generally known as mulm. The mulm must be syphoned or vacuumed out at regular intervals in order to avoid it passing through the biological filter and blocking the biological filter. If the pump is placed at the bottom of the fish pond, it will suck up much of the mulm and send it to the biological filter. The pump can be overworked in breaking up the mulm into fine particles. Once the mulm has been broken up into fine particles, it is very difficult to remove the fine particles at the filtration stage. The fine particles tend to find their way back into the pond and eventually the pond gives rise to a pollution problem. Still further, with a pump placed at the bottom of the fish pond, the inlet to the pump tends to become clogged and requires cleaning at regular intervals.

With gravity fed filtration systems, there are two types, these being known as wall drain gravity fed systems and bottom drain gravity fed systems. With a wall drain gravity fed system, it is still necessary to remove the mulm from the bottom of the fish pond. This will normally be done with one or more bottom drains which run to a discharge box which needs to be flushed at regular intervals in order to clean the pond. With a bottom drain gravity fed system, one or more bottom drains may be employed. The water is constantly drawn from the base of the pond and all the mulm goes with the water to the filters, and the water in the pond will always be clean.

The wall drain filtration type of system with its discharge box is suitable only for extremely large ponds.

One of the problems with this type of system is that the water around the drains is static and so, mulm will accumulate until the discharge box is flushed. This means that persons looking at the fish pond are able to see an unsightly pile of mulm in the pond and this unsightly pile of mulm becomes disturbed every time a large fish swims over it. Still further, fish such for example as koi will eat the mulm if they are hungry. Eating the mulm is a main cause of transfer of infection from one fish to another.

If a bottom drain filtration system is employed, then the mulm is constantly being transferred from the pond to the filter and therefore the pond will always be clean.

The fish will not have access to the mulm and this minimises the risk of infection from one fish to another.

However, in winter, it is preferable to draw the water for the filter from just below the surface of the water in the pond and for it to be returned at the same level. This is because the water is less cold at the bottom of the pond than at the surface. In order to so draw the water from just below the surface of the water in the pond, a wall drain is used. This gives rise to a problem in that the bottom drain is then not used for a long period of time and it has to be flushed out to waste periodically, and especially just before the bottom drain is put back into service. This is because there will inevitably be an accumulation of rotting debris underneath and around the bottom drain cover and in the drain pipe, making it possible to get a build up of harmful bacteria which could be detrimental to the health of the fish.

Another problem with bottom drain filtration systems is that in summer fish ponds tend to have a rapid growth of blanket weed which can block the bottom drain. Any form of restriction in the bottom drain is very serious in a well stocked pond. Blocking of a bottom drain presents problems because the water in the pond cannot be drained for access.

It is thus necessary for someone physically to get into the fish pond. An average fish pond with bottom drains is usually 4-6ft (1.2-2m) deep so that this becomes quite a task.

Most ponds do not have any form of in-built drains due to the high cost of installing such drains. A bottom drain filtration system is undoubtedly the best type of filtration system there is. However, a fish owner who acquires an existing pond which does not have any drains at all and wishes to add one, will probably find the difficulties presented by the installation of a bottom drain system to be insurmountable. For this to be done, the fish pond would have to be drained. If the fish pond is made of concrete, then the concrete has to be broken up in order to accommodate the pipe and the drain. This could weaken the structure of the fish pond and it increases the chances of future leaks. Another difficulty encountered may be the shape of the pond base. A drain needs to be located at the lowest point of the pond and there needs to be a gentle slope from the edge of the pond to the drain.

If there is no such gentle slope, then major re-shaping of the bottom of the pond is necessary because a bottom drain will not attract mulm from a point in the pond which is lower than the drain. If the pond is constructed with an inner liner laid directly on to an excavation, the risks involved with trying to install a bottom drain may be even greater.

It is an aim of the present invention to reduce the above mentioned problems by providing an economical and cost effective way of drawing water from the bottom of a pond such that mulm and/or dirt can be taken with the water in order to keep the pond clean.

Accordingly, in one non-limiting embodiment of the present invention there is provided a filter for filtering water for a pump for a pond, which filter comprises a housing, an inlet in the housing, an outlet in the housing, a hollow member which is in the housing and which is spaced apart from the housing to define at least one passageway along which water to be filtered passes as it flows from the inlet to the outlet, water flow control means which is in the housing and which is positioned adjacent the inlet; the hollow member having an apertured body which allows water from the passageway to pass to the inside of the hollow member, and an end at which water inside the hollow member is able to pass to the outlet; and the water flow control means comprising at least one chamber, and water flow control apertures which firstly cause the water to change direction and lose velocity in order to leave the chamber and which secondly cause the water to change direction again and lose velocity again as the water enters the housing after having left the chamber, whereby the filter is such that, in use, the water enters the housing from the chamber at a reduced flow rate which does not attract already separated solids whereby separated solids settle in the housing and filtered water passes through the hollow member to the outlet.

The filter of the present invention is able to handle relatively large volumes and high solids contents of mulm.

The mulm contains waste products and beneficial products.

It is necessary to separate these two products. The filter functions in three separate ways, with the first function being to receive the mulm and contain it, and then separate and segregate the mulm, the second function being to store filtered out waste products, and the third function being to filter beneficial products.

With regard to the first function, the filter preferably needs to be able to receive raw mulm, but in a manner which keeps the raw mulm separate from the main chamber. This may be achieved by having a separate entry chamber.

The beneficial products are mainly chemical and biological. Separation of the waste products from the beneficial products is achieved by gravity, and also the water absorbs the chemical content of the beneficial products as the water passes over and through the solids in the waste products.

As the flow changes, the water and solids change direction at different rates. As the flow expands and loses velocity, the water and solids expand and lose velocity at different rates.

In order to segregate the larger and heavier waste products, the filter uses the chamber. The filter is able to operate to control the water as it enters and exits the filter, and also as it enters and exits from a passageway adjacent the chamber. The chamber gives radial flow control of the water into the housing. The water flow control means, for example apertures, and optional nozzles, gives axial flow control of the water as it enters the housing from the chamber. The water flow control means makes it possible to control any desired flow or combination of flow between radial and axial before the flow enters a main chamber of the housing. The waste content is directed outwards in the flow. All this separation and segregation takes place before the mulm ever enters the main chamber of the housing.

With regard to the above mentioned second and third functions, as the treated mulm enters the main chamber of the housing, the treated mulm rapidly loses velocity and changes direction. The water loses velocity and changes direction immediately. The velocity and direction of the solid products is controlled by the water flow control means which acts as a separator, so the solid products do not lose velocity or change direction with the water content. The solid products content is heavier, it moves faster and in a different direction to the main flow. The solid products content cannot be attracted back into the reduced main flow it has just been directed out of. The solid products content may settle into a housing sump.

The lighter beneficial products are carried by the reduced velocity main flow, to be filtered through the hollow member.

The velocity of the water at the outlet is approximately equal to the velocity of the water at the inlet. However, the slower flowing water between the inlet and the outlet passes over the apertured body at such a slow rate that solids settle in the housing in order to give the required filtered water. The reduction in speed of flow of the water from the inlet is due to the use of the water flow control apertures which redirect the water such that it changes direction and in so doing loses velocity and slows down to the required amount to allow the solids to settle out.

The filter of the present invention operates such that the flow expands into the chamber and loses velocity and changes direction of flow. As mentioned above, if desired, flow control nozzles may be used. The flow control nozzles may control the velocity and direction of radial flow through 360°. Nozzles in the chamber may control the velocity and direction of axial flow through 360°. Nozzles in the chamber may control any combination of velocity and direction of flow between radial and axial, through 360°. The flow may expand losing velocity from the chamber, into the passageway. The direction of flow changes. The flow may expand, losing velocity from the passageway into the housing, and again the direction of flow may change.

The flow changes direction and gains velocity as it passes from the housing into the hollow member. The flow changes direction and gains velocity as it passes from the hollow member to the outlet. The velocity of the water at the outlet is approximately equal to the velocity of the water at the inlet. However, the slower flowing water between the inlet and the outlet prevents separated solids thrown outwards by the water flow control means being attracted back into the flow. Separated solids settle in the housing and the filtered water passes through the hollow member and through the outlet.

The filter may be one in which the separator has a plurality of the chambers and/or a plurality of the passageways.

Preferably, the filter is one in which the water flow control apertures cause the water passing from the inlet to the chamber to change direction by 90° so that the water enters the chamber in an axial direction and leaves the chamber in a radial direction. If desired, the water flow control apertures can cause the water passing from the inlet to the chamber to change direction by more or less than 90°.

Preferably, the filter is one in which the water flow control apertures cause the water passing from the chamber to the housing to change direction by 90° so that the water leaves the chamber in a radial direction and enters the housing in an axial direction. If desired the water flow control apertures can cause the water passing from the chamber to the housing to change direction by more or less than 90°.

The filter may be one in which the inlet and/or the outlet are constructed for receiving a manifold whereby the water flow in the filter can be fed from a plurality of different inlets and/or fed to a plurality of different outlets during use of the filter.

Preferably, the water flow control apertures are holes in a chamber wall defining the chamber. The holes may be circular holes but holes of other shapes, for example slots, may be employed if desired.

The filter may be one in which the water flow control apertures are formed in nozzles which extend outwardly from the chamber.

The filter may include a valve for controlling the flow of water into the housing and for preventing a back flow of water from the filter into the pond when cleaning the filter.

The valve is preferably a selectively adjustable valve. The valve is preferably a pivotally mounted flap valve. Other types of valve may be employed so that, for example, the valve may be an axially mounted spring biased valve or a solenoid valve.

The filter may be one in which the valve has external and/or internal adjustment means.

The filter may be one in which the apertured body is an open mesh body. Other types of body may be employed.

The filter may be one in which the inlet is at a first end of the housing, and which the outlet is at a second end of the housing. If desired however the housing may be of complex constructions with the inlet and the outlet being provided at other positions.

Preferably, the apertured body is of circular cross section. The apertured body may have other cross sectional shapes if desired so that, for example, the apertured body could have a square cross sectional shape.

The filter may include a flexible pipe for extending between the inlet and a chosen place in the pond, or for extending between the outlet and the pump. When the filter is provided on top or outside of the pond, then the flexible pipe can be used for extending from the inlet to the bottom of the pond. When the filter is positioned on the bottom of the pond, then the flexible pipe can be used for extending between the outlet and a pump located at the top of the pond.

The filter may include chambers and/or compartments in the housing to facilitate filtration. The filter may include chambers and/or compartments in the water flow control means to facilitate filtration. The filtration may be mechanical and/or biological and/or chemical.

The valve may be positioned in the chamber and at the inlet. Alternatively, the valve may be positioned in the housing and at the outlet. In another embodiment, the valve may be positioned outside the housing and at the inlet or at the outlet. If desired, the filter may be one in which there are two of the valves, one of the valves positioned at the inlet and one positioned at the outlet.

The filter may include a sump for receiving the separated solids.

The filter may include a vent device for venting air in the filter, for example to bleed off any air locks in the filter.

The filter may include a drain-off device for draining off water in the filter, for example before fully lifting the filter out of the pond for cleaning.

The filter may be one in which the housing is an openable housing for providing access to the inside of the housing.

The present invention also extends to a pump for a pond, the pump being provided with a filter of the invention.

The pond is preferably a fish pond but it may be another type of pond such for example as an ornamental pond.

The pump may be a submersible pump or an external pump. The pump may also be a sump pump.

The filter of the present invention is designed for constant use and easy maintenance. The hollow member is easily cleaned. The filter is such that it can be produced with only one moving part, namely the valve. The valve is able to open and close automatically. The filter of the present invention enables the pump and the filter to be situated at any convenient position inside or outside the pond, simply by connecting the flexible tube as appropriate to the filter. Thus the filter can be used to enable a pump inside or outside the pond to be used as a bottom drain or as a vacuum. Cleaning of the filter is especially easy since it is only necessary to take the filter out of the pond, open it, flush the filter out and then put the filter back in the pond. During this cleaning, the valve closes and prevents a back flow of water from the filter into the pond, thereby preventing dirty water in the filter going back into the pond.

Embodiments of the invention will now be described solely by way of example and with reference to the accompanying drawings in which: Figure 1 shows a fish pond with a known pump fed filtration system; Figure 2 shows a fish pond with a known wall drain filtration system; Figure 3 shows a fish pond with a known bottom drain filtration system ; Figure 4 shows a first filter of the present invention in a fish pond and being used in a first mode of operation; Figure 5 shows a second filter of the invention in a fish pond and being used in a second mode of operation; Figure 6 shows a third filter of the invention in a fish pond and being used in a third mode of operation; Figure 7 shows a fourth filter of the invention; Figure 7a is an enlarged view of a water flow control means part of Figure 7, and shows a valve of the water flow control means in a closed position and provided with adjustment means; Figure 7b is the same as Figure 7a except that in Figure 7b, the valve is shown in an open position; Figures 8,9 and 10 show three different types of water flow control means that can be used in the filter of the invention; Figure 11 is an exploded view of part of a filter of the invention; Figures 12,13 and 14 show three further different types of water flow control means that can be used in the filter of the invention; Figures 15 and 16 show a design of valve that may be employed in the filter of the invention; Figure 17 shows a fifth filter of the invention; Figure 18 shows a sixth filter of the invention; Figure 19 shows a seventh filter of the invention; Figure 20 shows an eighth filter of the invention; Figures 21,22 and 23 show three different variations to the eighth filter shown in Figure 20; Figure 24 shows a conventional bottom drain in a fish pond and illustrates how water is drawn directly off the bottom of the pond; and Figure 25 illustrates how the filter of the present invention can be used in a bottom drain mode and how water can be drawn directly off the bottom of the pond.

Referring to Figure 1, there is shown a fish pond 2 containing water 4 and having a known pump operated filtration system 6. The pump operated filtration system 6 comprises a pump 8 located near a bottom 10 of the fish pond 2. The pump 8 is connected by a pipe 12 to an ultra violet lamp device 14. The ultra violet lamp device 14 is connected by a pipe 16 to a biological filter 18. Water from the biological filter 18 is passed back to the fish pond 2 via a pipe 20. The filtration system 6 does not work that satisfactorily insofar as the pump 8 tends to suck up mulm (not shown) from the bottom 10 of the fish pond 2 and thus become clogged. Mulm that does pass through the pump 8 gets broken up into fine particles which passes through the biological filter 18 and tends to be re- introduced into the fish pond 2, thus giving rise to pond pollution problems. The biological filter 18 also tends to become easily blocked.

Figure 2 shows a fish pond 22 having a known wall drain 24 leading to a biological filter 26. The use of the wall drain 24 means that mulm (not shown) collects on the bottom 28 of the fish pond 22. This mulm is removed via pipes 30,32 which lead to a discharge box 34. The wall drain filtration system shown in Figure 2 is only suitable for large ponds and the accumulation of the mulm at the bottom 28 of the fish pond 22 causes problems. The mulm is unsightly which is visible to persons looking at the fish in the fish pond 22 through the water 4. The mulm is disturbed every time a large fish swims over the mulm, thereby clouding the water 4. Many fish such for example as koi will eat the mulm if they are hungry and this can lead to the transfer of infection from one fish to another. The mulm still has to be removed from the discharge box. This can be done by flushing the mulm from the discharge box 34 through a pipe 36 but it is wasteful of water and time consuming.

Figure 3 shows a fish pond 38 with a known bottom drain filtration system utilising a bottom drain 40. The fish pond 38 has a bottom 42 which slopes gently towards the bottom drain 40. The bottom drain 40 is connected by a pipe 44 to a biological filter 46. The bottom drain filtration system shown in Figure 3 is not entirely satisfactory in that it is extremely expensive to install, and it is not practical to install in an existing pond which does not have a filtration system. Because the water 4 is always taken off from the bottom 42 of the fish pond 38, the mulm (not shown) is always removed from the bottom of the fish pond and thus the water 4 in the fish pond is always clean. However, in winter, it is preferable to take water 4 from just below the surface of the water because this water is colder than water at the bottom of the fish pond 38. In order to enable this to be done, a wall drain 48 is utilised. This then means that the bottom drain 40 is not utilised and it can become blocked with mulm and general dirt and debris. It is thus necessary periodically to flush out the bottom drain 40 in order to avoid an accumulation of mulm and a possible build up of harmful bacteria which could be detrimental to fish in the fish pond 38. Still further, in summer, blanket weeds tend to grow quickly in the fish pond 38 and it tends to block the bottom drain 40. Clearing can be effected by physically getting into the fish pond 38 but since the fish pond 38 may be 4-6ft (1.2-2m) deep, this is quite a problem.

Referring to Figure 4, there is shown a filter 50 of the present invention in use in a first mode of use in a fish pond 52. The fish pond 52 contains water 4. The fish pond 52 is like the fish pond 2 shown in Figure 1. The filter 50 is connected to a pump 8 and the pump 8 is connected via a pipe 12 to an ultra violet lamp device 14, a pipe 16 and a biological filter 18 as in the filtration system 6 shown in Figure 1. Filtered water from the biological filter 18 passes to the fish pond 52 via the pipe 20.

As can be seen from a comparison of Figures 1 and 4, in Figure 1 the pump 8 is on the bottom 10 of the pond and this causes the above mentioned disadvantages. In Figure 4, the use of the filter 50 enables the pump 8 to be sited at the top of the water 4 in the fish pond 52.

Alternatively, a non-submersible pump 8 could be placed outside the fish pond 52 and then connected to the filter 50 by an appropriate pipe.

In another embodiment a non-submersible pump and the filter could be placed outside the fish pond, and connected by an appropriate pipe in the pond.

The filter 50 is shown provided with flexible pipe 54 which sucks water and mulm from the bottom 10 of the fish pond 52 as shown by the arrows 56.

Figure 5 shows another filter 58 of the present invention used in a second mode of operation in the fish pond 52. Similar parts as in Figure 4 have been given the same reference numerals for ease of comparison and understanding. As can be seen from a comparison of Figures 4 and 5, the filter 58 is slightly differently shaped to the filter 50. Also, the flexible pipe 54 is connected between an outlet side 60 of the filter 58 and the pump 8.

Figure 6 is a side view of the filter 50 being used, with the flexible pipe 54 being connected to a surface skimmer arrangement 62 for skimming debris from the surface of the water 4. The pump 8 can be connected via line 12 to the other parts of the filtration system shown in Figure 4.

Referring to Figure 7, there is shown in detail a filter 60. As can be seen, the filter 60 comprises a housing 64 having an inlet 66 and an outlet 68. A hollow member 70 is provided in the housing 64. The hollow member 70 is positioned in the housing 64 as shown in order to define a main chamber 65 along which water to be filtered passes as it flows from the inlet 66 to the outlet 68.

The filter 60 also comprises water flow control means 74 positioned adjacent the inlet.

The hollow member 70 has a first end 76 which is blocked by the housing 64 as shown and which acts to block the flow of water from the inlet 66 into the hollow member 70. The hollow member 70 also has an apertured body 78 which allows water from inside the housing 64 to pass to the inside of the hollow member 70. The hollow member 70 also has a second end 80 which allows the water from the hollow member 70 to pass to the outlet 68.

The water flow control means 74 comprises a valve 82 for closing the inlet 66. The valve 82 acts to prevent a back-flow of water from the filter 60 to a fish pond during cleaning of the filter 60.

The water flow control means 74 also comprises a chamber 84 in which the valve 82 operates, and water flow control apertures 86. The water flow control apertures 86 cause water from the inlet 66 to pass from the chamber 84 to the passageway 72 and then from the passageway 72 to the main chamber 65 such that the water changes direction and in so doing loses velocity. The loss of velocity is to such an extent that the water which passes over the hollow member 70 flows sufficiently slowly for solids in the water to settle in the main chamber 65 of the housing 64. The filtered water is able to pass through the apertured body 78 and then through the outlet 68 for being returned to the pond.

The water flow control apertures 86 cause the water from the inlet 66 to change direction by 90° so that the water enters the chamber 84 in an axial direction and leaves the chamber 84 in a radial direction. The water flow control apertures 86 cause the water from the chamber 84 to change direction by 90° so that the water enters the passageway 72 in a radial direction and leaves in an axial direction. The water flow control apertures 86 are circular holes in a chamber wall 88 defining the chamber 84.

The apertured body 78 is a open mesh body. The open mesh body can be made of wire of a plastics material.

The valve 82 is a pivotally mounted flap valve which is pivotally mounted by a pivot 90.

The filter 60 shown in Figure 7 operates on the basis that the mulm on the bottom of a pond will contain both beneficial products and waste products. The filter 60 operates to separate the waste products from the beneficial products. The filter 60 operates with a two stage filtration. At the first stage the beneficial products and the waste products are separated. At the second stage, only the waste products are filtered out.

The first stage separation is enabled because the waste products are larger and heavier than the beneficial products. The water flow control means 74 acts to control the direction, velocity and turbulence of both the water and the solids in the water passing through the water flow control means 74. The water flow control means 74 is used to separate the waste products from the beneficial products in the mulm. The control is used to segregate the waste products in the water. The various stages of separation in stage 1 are as described hereinbelow.

In Figure 7, the valve 82 may be provided with adjustment means, for example adjacent the pivot 90. The adjustment means is for controlling the degree of opening of the valve 82, and thus for controlling the flow rate of water through the inlet 66.

Figures 7a and 7b show the water flow control means 74 of Figure 7, and provided with adjustment means in the form of an adjustment screw 91. The adjustment screw 91 is able to act on the valve 82 to control its degree of opening, as can be seen by comparing Figures 7a and 7b. Controlling the degree of opening of the valve 82 in turn controls the flow rate of water through the inlet 66.

SEPARATION OF MULM Solids enter the chamber 84 and separate as they change direction and lose velocity. The solids separate as they divide between the water flow control apertures 86.

The solids enter a passageway 72 around the water flow control means 74 and separate as the solids change direction and lose velocity. The solids then enter the main part of the housing 64 and separate as they change direction and lose velocity.

SEGREGATION OF WASTE PRODUCTS The waste products are larger and heavier than the beneficial products. By having control of the flow direction, velocity and turbulence, the waste products are directed outwards in the flow.

DIRECTION OF FLOW CONTROL The flow of water enters the water flow control means 74 chamber in an axial direction, and leaves in a radial direction through the apertures 86. The flow divides into the various apertures 86. Nozzles (not shown) may control radial flow into the passageway 72. The nozzles may control axial flow along the passageway 72. The nozzles may control a combination of flows between radial and axial directions. The flow of the water enters the passageway 72 in a radial direction through the apertures 86 and leaves the passageway 72 in an axial direction.

VELOCITY OF FLOW CONTROL The flow enters the chamber 84 in the housing 64 and expands, losing velocity. The flow enters the passageway 72 and expands, losing velocity. The flows enters the housing 64 and expands, losing velocity. The flow enters the hollow member 70, reduces, and increases velocity. The flow enters the outlet 68, reduces and increases velocity.

TURBULENCE OF FLOW CONTROL At each of the three major changes in direction of flow, the flow expands. The three major changes in direction of flow occur in the chamber 84, the passageway 72 and the housing 64. This expansion reduces turbulence to a minimum. The lowest turbulence is in the main chamber 65 of the housing 64.

The above mentioned second stage filtration of the waste products only is by two methods as follows.

GRAVITY The slowest velocity is combined with the slowest turbulence in the housing 64. Waste products thrown outwards in the flow by the separator are not attracted back into this reduced flow. Waste products settle in the main chamber 65 and settle to the bottom of the housing 64.

MECHANICAL The beneficial solids are filtered by the hollow member 70.

Referring now to Figures 8,9 and 10 there are shown three different types of water flow control means 74. The water flow in Figure 8 can be seen by arrows 92. Figures 9 and 10 are such that the water flow control apertures 86 are provided with nozzles 94. The nozzles 94 give a flow as shown by arrows 96,98. The arrows 92,96,98 are such that the solids part of the flow is indicated by dark parts of the arrows, whereas water containing less solids is shown by lighter parts of the arrows.

Figure 11 is an exploded view of the water control means 74. As can be seen, the water flow control means 74 comprises the valve 82 located in a short tube 100 which contains the chamber 84, the waterflow control apertures 86 and the chamber wall 88. A tube portion 102 fits into the right hand end of the tube 100 and is used to provide a pipe connector portion 104 of reduced diameter as compared with the diameter of the tube 100. The valve 82 is provided with an O-ring 106 in order to make sure that it is a good fit in the tube 100.

Referring now to Figures 12,13 and 14, there are shown three further different types of water flow control means 74. These water flow control means 74 are able to direct the water flow in different directions as will be appreciated from Figures 12,13 and 14.

Figure 15 and 16 show a valve 118 which is an alternative to the valve 82. The valve 118 has a body 120 which slidably mounts a shaft 122 of a valve element 124 having a head 126. The head 126 has a chamfered portion 128 which locates as shown against a seal 130 located against an inwardly projecting lip 132 formed as part of the body 120. The valve element 124 is biased to the closed position shown in Figure 16 by a spring 134.

Figure 17 shows a filter 134 having a large sump portion 94.

Figure 18 shows a filter 136 which operates in a vertical position. Again, similar parts as in previous Figures have been given the same reference numerals.

Figure 19 shows a filter 138 which is like the filter 136 shown in Figure 18 but which has the valve 82 and the chamber 84 at a different position. In Figure 19, the waterflow is opposite to the waterflow in the filter 136 of Figure 18, as can be appreciated from the positioning of the inlet 66 and the outlet 68. In vertically positioned filters as shown in Figures 18 and 19, the separated solids will collect at a bottom part 142 of the housing 64.

Figure 19 also shows the use of lips 144,146 for directing filtered out solids away from the surface of the apertured body 78 as they fall towards the bottom part 142 of the housing 64.

Figure 20 shows a filter 140 which is designed to operate vertically and which has a frusto-conical housing 64 as shown. The inlet 66 and the outlet 68 are positioned as shown. Similar parts as in previous Figures have been given the same reference numerals for ease of comparison and understanding. The passageway 88 in Figure 20 is larger than in previous Figures. The filter 140 has a plurality of inlets 66 as shown and water passes along a manifold 152 to the chamber 84.

Figures 21,22 and 23 show three different variations to the filter shown in Figure 20. As can be seen from the arrows 148, the water is able to enter the filter of the invention in different ways at a bottom part of the pond 38.

In Figure 21, the filter shown is able to free stand on the bottom of the pond and no manifold or anything else is employed. The end 76 of the hollow member 70 is spaced apart from the water flow control means 74. The end 76 may be blocked, open or provided with apertures. The outlet 68 is provided with the valve 82, this being instead of providing the valve 82 in the water flow control means 74.

In Figure 22, the inlet is at the base as shown and also at one side. The side inlet may be a second bottom drain or a vacuum inlet. The bottom or side inlet could be capped or plugged, making a multiple choice filter suitable for any position in a pond, between the bottom and the surface of the pond. The filter may be used for any purpose, from use in a bottom drain pond, to a walled drain pond, to a vacuum arrangement.

The filter shown in Figure 23 is similar to the filter shown in Figure 22 but has inlets at its bottom and both of its sides.

Figure 24 shows the bottom 40 of the pond 38 shown in Figure 3, and illustrates the presence of a drain cover 154 and the passage of water downwardly as shown by arrows 56.

Figure 25 shows the bottom 10 of the fish pond 52 shown in Figure 4 and illustrates how the flexible tube 54 sucks the mulm off the bottom 10 and upwardly as shown by arrows 56. The bottom of the flexible pipe 54 can be provided with a central obturator 158 which can be of curved design as shown in Figure 25 or of a more conical design as shown in Figures 4 and 5.

It is to be appreciated that the embodiments of the invention described above with reference to the accompanying drawings have been given by way of example only and that modifications may be effected. The filter of the present invention is able to give good mechanical filtration to any fish pond. Ponds other than fish ponds may also be filtered if desired. Thus, ornamental ponds including fountains and waterfalls may advantageously be filtered so that particles can be filtered and thus help to stop the pump from prematurely blocking up and/or wearing.

The filter is able to run continuously throughout the entire year. Thus the filter can be run in winter even although the fish in the fish pond normally do not feed.

The winter running helps to keep the water in the pond cleaner than it would otherwise have done and it also helps to prevent the formation of ice on the surface of the water, thereby allowing more oxygen to enter the water than would be the case if the ice were present. Other types of pumps than those illustrated may be employed so that, for example, the pumps may be sump pumps or external pumps.

In addition to giving good mechanical filtration to ponds, the filter of the present invention may also give good biological and/or chemical filtration. The biological filtration may be provided by using the filter with a pump to suck from the bottom of a pond where ammonia usually lies if the pond contains fish. The biological filtration may also be provided by forming the inside of the housing with a rough or dimpled surface for facilitating the collection of bacteria for causing biological filtration.

Gravel or the like may also be provided in the housing to promote biological filtration. Chemical filtration may be obtained by adding appropriate chemicals in the housing, for example in the form of rings, blocks or stones in a sump part of the housing. The housing may be shaped to have special compartments for effecting biological and/or chemical filtration.