Tiny Fish that Rock!

They're not coldwater in the same sense that, say, trout are; pygmies mostly live in the coastal plain of the southeastern US, so 'subtropical' would be closer. They're not actually closely related to bluegill and other centrarchid sunfishes, which are bigger, tougher fish that live in a wide range of temperature conditions. I kept my pygmies at room temp.
 
Notophthalmus is correct. I call them "cool" water (not cold), because they generally don't prefer tropically warm tanks, but they are not so much like many of the game fish you might think of. I keep mine in my basement and most of the year the tank it around 70-74F. Above 80F seems to be stressful for them. During the winter the tank gets down to about 65F and they continue to breed. They can handle cooler temps as well, but it's not optimal and they don't normally experience the frigid temps we in the Midwest get.

Research on Elassomids (the pygmy sunfish group) right now suggests they are more closely related to Sticklebacks and such over perch-type fish.
 
they are butiful fish! may have to track some down... :)
 
They are notoriously delicate/sensetive fish, so they're going to need a tank of their own, and they REQUIRE small live foods like bbs, grindal worms, micro worms, etc. Glassworms, adult brine shrimp, and bloodworms are too big. Fortunately, because of their size, a 5 gallon is big enough to keep and breed a small group.

Are you referring to babies here, or do adults need tiny live foods as well?
 
Adults require small live foods as well. Take a look at the photos as you'll know what I mean. Their mouths are pretty small, and the adult fish itself is only 3/4". The babies, on the other hand, need microscopic foods.
 
I kept mine on Ceriodaphnia and the occasional small midge larvae. I haven't tried babies; you'd probably need to get a green water/ rotifer culture going, or at least regular additions of pond water to the tank.
 
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