Danios are very active swimmers. Imo, a 3 gallon container is insufficient to say the least, due to a lack of swimming space more than bioload, although that might come into play as well and prevent you from keeping them in a school of adequate size. From what i understand, they are fairly tolerant of cooler water, but would do better with a heater. The pink danios are likely the genetically engineered "glowfish", the ones i've seen had a reddish or pinkish tinge. Yes, the zebra, leopard, and blue danios all have long finned varieties, possibly other danios as well.