Top view of upflow filter

Biological Filter

Upflow or downflow, which is better? We don't know.

We chose the upflow filter because it fit better in our design. We have limited space for the pond, so we decided to raise the filter off the ground and let the water spill back down into the large pond. An upflow filter had to be high enough so that the top of the filter was above the height of the start of the stream. A downflow filter would have had to be higher so that the bottom was at the top of the stream. I decided that would make the filter much too dominant, visually, in the garden.

top view including flow to stream The other design concern we had was how to get the water from the filter to the stream. The image to your left shows a pipe from the filter to the pond. That was a temporary arrangement. We wanted to start filtration immediately, but the concrete had to dry. The pipe kept the water off the concrete. When we removed the pipe, I realized exactly how much a short piece of white plastic pipe can dominante a scene.

top view including flow to stream Unfortunately, the ugly pipe fitting at the filter end was there to stay. I wanted to cover it with a piece of bamboo, but bamboo like that, in a single, short length is hard to find. In the end, Robert cut a larger pipe, painted it with that marbling spray paint and put the pipe over the pipe fitting.

Click for a schematic of our filter. It is not to scale.

Parts List
QuantityDESCRIPTIONPRICE ($)
1 30 gallon plastic tub 10.00
5 gallons plastic bio-balls 25.00
5 gallons quarter inch lava rock 2.00
16 squar feet filter medium 10.00
20 feet half inch flexible water tubing 0.14 per foot
16 squar feet aluminum screen 4.15
3 one inch threaded bulkhead fittings 5.29 each
2 quarter inch flourescent light panels 8.49
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This page was last modified Thursday, 02-Sep-1999 08:04:10 PDT