I set up a low tech 40 gallon fwpt about 2 years ago, poor choices and minimal maintenence have reduced it to a very dense algae farm I can live with that, still enjoy having the fish. Anyway over a year ago I managed to eradicate the original snail infestation, small round guys. I relentlessly killed them off until they were gone and they stayed gone. I have not added anything to this tank in at least 6-8 months; no fish, plants or live foods of any kind. All of a sudden there are hundreds of small conical shaped snails, not the same species as before. Huh ? Never had them before.
WHERE did they come from ???????