Viewing post #2728600 by ElPolloDiablo

Suzume said: It's an indoor pond. The tiny snails were introduced with a plant added for "vegetables". I do know those tiny snails do carry diseases but I think the snails are all gone now. Now veggies are chard and lettuce leaves. I do have outdoor ponds and have never had snail or algae problems in them. The turtle eats the inside algae when it grows. No herons but raccoons are a problem. We always used ground level hot wires to keep the herons out (when I lived in an area with a heron problem).

My big concern now is if the diseased fish are gone and the snails are gone, is the water "clean"?

Replace the water in the pond and clean the sludge at the bottom (put it in the compost pile, it's good stuff): it's something that should be done once in a while with any small pond even if you have a very good filtration system. It will take care of any pathogen you may conceivable have and you sill be able tosee if any "alien" is present.