I have a 5 gal tank with led and filter, what kinds of fish can put in there? and how many of them? i can get a heater if neccessary, but would prefer a cold water tank. I just want happy fish(s) in a humane enviroment. Inwas thinking about penguin tetras- but I'm not sure if they would work for the size. ANY ADVICE POSSIBLE ABOUT FISH CARE IS APPRICEATED. I have been doing alot of research and it seems like everyone has a different opinion on what is humane and not, so I'm really confused and just really dont want to kill my fish(s)