How to Build a Goldfish Pond Filter

Ensure the connectors and water lines fit together. There will be one set that links the pump line to the smaller bulkhead and links the PVC pipe to the other side of that bulkhead. There will be a second, larger set that link the second bulkhead to the hose line. Ensure the elbow joints fit the PVC pipe. Take everything apart once the fit has been checked.

Take the smaller bulkhead apart and place the hard side with the washer against the outside of the storage tub, about an inch from the top along one of the shorter sides, if applicable. Centralize the bulkhead so that it is equally spaced from the both adjacent sides and use the marker pen to draw a circle on the tub, using the bulkhead as a guide.

Use the utility knife to cut the circle away. Cut small and carefully widen the circle. Remember, a smaller circle can be widened but a circle that is too large is there to stay. Fit the bulkhead into the hole, ensuring the rubber side is on the inside of the tub and the washer is on the outside. It should be a very snug fit.

Repeat steps 2 and 3 with the larger bulkhead, on the opposite side of the tub.

Connect the small connector to the outside of the smaller bulkhead and attach the pump line. This can be silicone in place for security, but doing this will make cleaning the filter more difficult.

Connect the second small connector to the inside of the same bulkhead.

Connect the larger connector to the outside of the larger bulkhead and fit the hose line.

Move the filter into the desired location and run the hose line until it reaches your desired location in the pond. The filter will be most efficient if the hose line moves downward from the filter and does not lead over higher terrain. Use the marker pen to mark where the hose line should end and then bring it back from the edge of the water and cut the hose line to size.

Repeat Step 8 with the pump line. Locate the pump away from the hose line and mark the required length on the pump line. Cut the excess pump line off with the craft knife. There must be enough pump line to reach from the filter to the bottom of the pond, where you will situate the pump.

You will now make the internal plumbing for the filter. If possible, attach an elbow join directly onto the internal connector on the smaller bulkhead. If this is not possible, cut a short length of PVC pipe to link the connector and elbow joint. Attach the elbow joint so that the free end points directly down into the filter. Measure from the bottom of the joint to about 2 inches from the bottom of the filter. Measure a length of PVC pipe to match this measurement and cut with the utility knife.

Attach the new length of pipe to the elbow joint so that it reaches into the bottom of the filter. Attach the second elbow joint to the length of pipe so that the free end joints directly across the base of the tub and faces the opposite side. Measure from the end of this elbow joint to the opposite edge of the tank and subtract the length of the PVC pipe end cap. Mark and cut a length of PVC pipe to fit this. Attach the end cap and ensure a tight seal. Silicone on if necessary.

Mark a series of evenly spaced dots along one side of the length of pipe, stopping at the middle. Do the same on the opposite side and end of the pipe. There should now be a line of dots all the way along the pipe, half on one side and half on the other. Clamp the pipe to the work bench and drill through these dots with the hand drill, ensuring that the drill only penetrates one side of the pipe.

Attach the drilled pipe to the elbow joint at the bottom of the tub, ensuring that there is around an inch between the bottom of the pipe and the bottom of the tub.

Cut sheets of coarse sponge equal to the length and width of the tub. Cut one sheet in half and subtract the diameter of the PVC pipe from its width. Place one sheet on the bottom of the tub, under the PVC pipe. Place the two smaller sheets on either side of the pipe. Continue to place sheets until one-third of the tub is filled. You may need to cut small sections from the sheets to allow for the vertical PVC pipe, but ensure the sponges are a very tight fit in the tub.

Cut similar sheets of the fine sponge to fill the second third of the tub. Ensure it is a tight fit. Any gaps around the side or the PVC pipe will allow water to escape without being properly filtered.

Fill the final part of the tub with the bio-balls. These can be loose or placed in a mesh bag. Ensure they cover the sponge in a thick layer but allow for some movement. Ensure no bio-balls can clog the larger bulkhead. Use a thin layer of mesh over the bulkhead opening and silicone in place if necessary.

Ensure the filter is in your desired location and attach the pump line to the pump. Place the pump in the bottom of the pond and run the hose line from the filter to the desired output location. Plug the pump in and check that the filter is working. Water should pass down the pump line into the PVC pipe, down to the bottom of the filter and then slowly fill the filter before it reaches the second bulkhead and falls down the hose line back into the tank.

If the pump is too powerful, the tub will fill faster than the water can drain out. The watertight lid on the tub will prevent leaks but it may be necessary to adjust the pump to provide a slower flow rate.

Check and clean your filter every month. Fill a bucket with pond water and turn off the pump. Remove the bio-balls into a second bucket and gently rinse the sponges in the bucket of water. Empty any sand and accumulated detritus from the bottom of the filter and use bottle brushes to clean out the pipe work. Place the filter back together again and turn it on.