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We are building a simple in-pond two unit filter out of virgin 55 gallon plastic barrels. It could also be used outside of the pond by gravity feeding to the first barrel instead of cutting slots. If so, make sure the top of the barrel is not too far below the pond level. This is to make sure if there is a power outage the pond will not gravity drain dry, but only until the pond level is even with the top of the barrel. These barrels were purchased from Sam's Club for $23 each. The 1st barrel is a settling unit to settle the heavier solids out. With the in pond arrangement it is also a skimmer. There is an option to add vertical filter brushes hung from the top on PVC piping. The bottom gunk will be pumped out with a portable pump to waste. The 2nd barrel will have 2 layers of horizontal filter matting material supported on top of a bar-b-que grill grating 12 inches from the bottom (to filter out finer particles that won't settle in the 1st barrel); the bottom 12" section with the submergible pump will be filled with lava rock or wet fired ceramic material to act as a biological filter section.
Step 1 - Cutting the top open and cutting lower hole for the 1 1/2" bulkhead connection to the valve manifold. The 1 1/2 inch bulkheads are $25 each.
Step 2 - Cutting 2nd top open and cutting 2 upper holes for 2 - 1 1/2" bulkheads (2" bulkheads are $52, 3" bulkheads are $101) to connect the two barrels together. Ideally the bulkheads should be one size larger than the pipe manifold, or use 2 the same size. Otherwise the water level in the pump barrel will drop about 2-3" lower than the pond, and the barrel will start to float up.
Step 3 - Cutting 12 - 1/4" by 5" skimmer slots in the 1st or settling barrel that will allow water in, but will keep small fish out. This assumes the top of the barrels will be above the high water line. Leaves will be pulled from the slots. Be sure the "underwater" square area of the slots are about twice the square area of the pipe manifold. You can stagger the height of the slots to allow for changes in water level. Otherwise the barrel water level will be 1-2" lower than the pond water level, and the barrel will start to float up. The solution to this is to add heavy plant containers to the top of the barrel if necessary.
Step 4 - Assembling the bulkheads, unions, and valve manifold components. The valve manifold is 1 1/2 inch with 4 - 3/4 inch T's to feed 4 - 3/4" black poly tubing lines. Be sure the total square area of the outlets are about the same as the square area of the pipe manifold diameter, or the square of the diameters. For instance, 1.5" squared is 2.25" and 3/4" squared is 9/16" * 4 = 2.25". The actual square area of the 1.5" manifold is 1.77 square inches. The 3/4" black tubing goes to aeration outlets. The end 3/4" valve will allow a flowing current in the pond through a garden hose connection, which can also be used for water changes to waste.
Step 5 - Assembling the inside pump connection in the 1st barrel. The off-center cam-like pump arrangement allows the pump to be rotated to rest on the bottom of the barrel or "water lily basket". This submergible pump is an Oase Aquamax 10,000 which delivers 2,100 gallons per hour (GPH), consumes 100 watts, and comes with a limited 3 year warranty.
Step 6 - Make sure the union arrangement will work for the pump being connected directly to the valve manifold. This is handy for bypassing the filter or emptying the pond whenever necessary, or at least lowering the level well below the intake slots.
Step 7 - Support base of 1/2" PVC tubing to support filtration media. Be sure to drill holes in the top of the 3-way PVC connectors to prevent the support from floating. Ceramic or lava rock is inserted to supply biological filter media. Water lily porous basket used to keep rock away from pump.
Step 8 - Pump completely enclosed by porous baskets, ready for more lava rock to be added around filter to complete biological filtration section.
Step 9 - Weber nickel coated steel bar-b-que grill grating will support filtration media. 22 1/2" diameter grating was $11.97 at Home Depot.
Step 10 - Filtration media support in place.
Step 11 - Filtration pads cut to 1/4" oversize or 23.25 inches in diameter.
Step 12 - Filtration pads in place.
Step 13 - Another view of filtration pads in place. We expect this filter, with a filter media area of 424 square inches, to handle 3/4 pound of dry fish food per day, and provide enough aeration to heavily overload a 2,000 gallon pond with 100+ Koi from 6" to 2 feet. In other words, well over 900 Koi inches. The old filter was an 18 gallon trash basket (1/3rd the size of the 55 gallon drums) with a filter media area of 143 square inches, and a 4,100 gallon per hour Little Giant pump which consumes 700 watts. Although it supplied enough oxygen, it was only able to handle 1/4 pound of dry fish food per day. Any more and the ammonia and nitrite levels started to rise. So together the pumping rate is 6,200 GPH, consuming 800 watts, which means we are turning over the water in the pond every 20 minutes or almost 150,000 gallons per day! We plan on replacing the Little Giant pump with an Oase 15,000 Aquamax which will deliver 3,900 GPH at a cost of 260 watts, saving 440 watts per hour, or 10.5 kilowatt-hours per day (a savings of about $33/month or $400/year). Then the total pumping rate through 4 square feet of filter media will be 6,000 GPH at a total cost of 360 watts per hour, or 8.6 kilowatt-hours per day (total cost about $27/month or $325/year). Both pumps could be run off a car battery's 110 volt "rectifier" (available from camping or motor home supply stores) in an emergency. |
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