| My own experience with sand filters: I just (last weekend) got rid of my 2 oversized Hayward sand filters that have been a part of my pond since I began pond-keeping in 1997. Lately, the top layer of sand in each of the sand filters would get coated with a solid sheet of the same green algae that covers the entire concrete surface of the pond, itself –fine in the pond, but not the filter. On a weekly basis, I had to pull off the multi-port valve on top and physically scrape out the sheets of algae. (The pressure would keep building and building and, one time, two of the elements at the bottom actually broke off, letting all that cruddy sand go back into the pond.). I now have two Aquabead filters, in addition to three 250 gallon up-flow filters, which are strictly for bio-filtration. So far, after only 3 days with the Aquabeads, the water quality "looks" much better and the fish seem to be much more comfortable.
You mention bio balls in a sand filter. I tried that at one time, too, and wound up with a huge, stinking, anaerobic mess. It MIGHT be all right, if you have a blower on the filter and use it on a regular basis to break up the sticky pack of the bio balls. I didn’t, and it wound up costing the lives of several nice fish, in spite of my best efforts at maintenance. |