Many people enjoy looking at the clean, clear water in their pond. However, if nature fills your pond with green algae and other unwanted bacteria, then you can build your own pond skimmer or filter by submerging a homemade tank in your pond. The tank is designed to pull in water from your pond, swirl it through a filtering system, trap the algae and bacteria, and release the clean water back into your pond.
Remove the plug from the round stock tank and cover the drain with Teflon tape so it won’t leak. Put back in the plug and screw it in tightly.
Draw a circle on the flat front area of the tank, the same circumference as the closet flange (4 inches) and use a small hand saw to cut out this hole. Use the closet flange as a template and drill out the mounting holes in the tank--four or six depending on the closet flange. Cut a circle piece of the egg crate grate the same size (4 inches) and place it inside the closet flange.
Apply silicone on the outside surface of the tank, around hole you cut, and then place the closet flange in position over the hole and on top of the silicone. Insert screws into the holes you drilled and screw the closet flange onto the tank.
Use the handsaw to cut two lengths of PVC pipe to create a T-shape that will lay flat on the bottom of the tank with the "T" and elbows attached. Attach the "T" to create the T-shape, and then attach the elbows facing in different directions to create a swirl effect in the water.
Cut the grate so it will fit horizontally inside the tank, and then cut a hole in the centre of the grate. Place the upturned tail of the T-shaped PVC into the hole in the grate. Place the grate and connected PVC pipe into the tank.
Lay the filter media loosely on top of the grate, enough to fill up to the top of the tank. The best filter media is a fibrous material like scrubber pads.
Attach another PVC elbow to the top of the PVC pipe sticking out on top, and then attach a sump pump hose to the elbow. Locate the sump pump as far as possible from your skimmer to allow good circulation. Attach the pump hose to the pump, and start filtering your pond.
The round shape of the tub creates a whirling effect of the water, which promotes better filtering than a square or rectangular-shaped tub.