Check out the North American Native Fish Association for the best advice on this one.
Chrysotus are wonderful aquarium fish. They are moderately aggressive feeders, but very peaceful toward tankmates. True to their name they will pretty much stay right at the top much of the time, leaving lots of space below for others. They do get a little big (4" is the biggest I've seen) - a 30 is the smallest tank I would keep them in. They do school, and would prefer to be in a group of four or more.
Bluefins are finicky eaters. I was never able to keep them on flake, but if you are willing to feed frozen or live they are also great little fish. Keep in mind that they only show their most brilliant colors for a few weeks of spawning, but for that time they put to shame any neon tetra. Dominant males will retain some color year-round though (typically the reds and yellows, with the characteristic blues fading). They really appreciate some rooted plants. They also school, really wanting a group of six or more.
Both are good community fish.
The best information on the web will be found under the Latin names (Fundulus chrysotus, Lucania goodie). Best common names to search are golden topminnow and bluefin killifish.
