I've been wanting to keep Gulf killifish (Fundulus grandis) or Mummichog (Fundulus heteroclitus) for a while and was wondering if there is anywhere to order live ones that could be shipped to california? Also are there any tips for keeping or breeding these fish? I'd be keeping them at room temperature. I think I found a source of Mummichog, but worry that they might not doo well at room temp since they'd be shipped from maine

I have had luck in keeping and breeding these in warmer temperatures.  I have worked with several batches of gulf killifish and bred them in a 55 gallon tank using extra long spawning mops, picking the eggs, and water incubating with a bit of methylene blue.  I added plastic plants for structure for the fry and had success with both powdered and live foods for the fry.

Since the ideal water temperature for Killifish is between 72 and 75F, they can do well at room temperature and you may not need a heater if you keep them at this steady temperature. You should prepare a spawning tank that only needs a heater, a sponge filter, and a mop for spawning fish. Some recommend turning off the lights in the aquarium to allow them to breed better but I have also had success providing adequate light.