I have read all the caveats and warnings about them, but so far my pair of "freshwater" flounders are doing well. I have had them for a couple of months now. Since they are TINY babies (they are only like 1.5 inches now and were smaller when I bought them) and I did not expect them to survive, they've been living in a 2.5 gallon brackish (marine salt, not freshwater salt) tank with just a horned nerite snail for company and some planted water sprite for shelter. They spend most of the time buried in the sand (fine-grain Petco brand freshwater aquarium sand--highly recommend) but occasionally sit under the plants or stick on the glass. They eat very little and so I am careful not to put too much food in the tank. I siphon out waste and uneaten food and change a third of the water weekly, using air line tubing as my syphon tube. I couldn't tell you how much salt I'm adding, as I really just eyeball it, but I have a hydrometer in the tank to make sure I'm not adding enough to make it saltwater. I feed them live bloodworms sometimes but they eat the frozen ones happily, and sometimes they get frozen brine or mysis shrimp, but they prefer bloodworms. So far they will not eat pellet food, not even Hikari carnivore sinking wafers (broken into tiny pieces, of course). My only question is, will they be okay if I only feed them bloodworms (until they get a bit bigger, at least) or do they need a more varied diet to get all their nutrition? Because bloodworms are the only food they eat fully and consistently.