the ''freshwater'' flounder is a brackish to full marine fish. as they get older they will require a salinity of about 1.020. they get about 6-7''. they will eagerly accept live brine and blackworms and with time and patients, they will accept frozen bloodworms, brine, mysis, and krill for adults. Ive actually been able to get them eating NLS thera A at my store. Usually when you see the word ''freshwater'' in front of a fishes name it means there brackish IE: freshwater lionfish, freshwater moray eel, freshwater pufferfish. sure they'll survive for a short time (2-3 monthes) in freshwater, but for long term health they will NEED brackish or full marine conditions like the ''freshwater'' Moray Eel. if kept in freshwater for to long they will just wither away and die.