Sudden decrease of water quality and snail invasion
I replaced the fine filter three days ago, and today I noticed the water has turned over, that there is a snail invasion (which was not the case three days ago), and that the plant leaves have plenty of black, long algae (which also was not the case three days ago). Please tell me what I should do.
this sounds as if a dead animal (a fish or a larger snail?) is lying in the aquarium decomposing, which heavily pollutes the water. Generous (!) partial water changes are advisable in any case, also the tank must of course be checked for a possible dead animal.
Further measures are probably not necessary at the moment; if required you can simply siphon the snails off during a water change.
Dr. Bodo Schnell