| Steve: I agree that water hyacinth would be an excellent way to go if someone wanted to try to implement a true plant filter. When I was a teen, I raised tropical fish in little swimming pools sunk into the ground. Water hyacinth were the only filtration. The roots would fill the pool, becoming loaded with mulm and debris. It was a very effective mechanical filter. I removed about one-fourth per week and sold to a local shop. I'd remove the oldest, largest ones that were getting yellowing leaves. Looking back, it worked pretty well for what I was doing .... there were likely no more than 2 fish per plant (grown from initial free-swimming fry to maybe 2" (larger on Gouramies) marketable size). I did not do much water testing back then, but the parameters must have been pretty good because I grew out better fish than the tropical fish shops carried in stock. Applied to koi, I guess it would take thousands of hyacinth per fish to be equivalent.
To have an effective water hyacinth filter, no more than 6" of water depth would be needed, but the surface area would have to be huge. I think the goal would be to remove as many hyacinth daily/weekly as matches the weight of food/leaves/etc entering the pond ... all on a dry weight basis. ....For those not familiar with water hyacinth, when dried a plant is as light as a feather. I think there would need to be a bottom drain for the settlement to be discharged. It would be interesting to see what someone could accomplish pursuing a truly scientific approach to a plant filter, but I think it would prove to be far more work than anyone would care to undertake. |