I agree- the bigger the better. 20G is fine for a krib pair but more is better. I advise Danios because they are way too quick and stay at the surface whereas Kribs stay at the bottom. This way even if the Kribs do breed, and become murderous, the Danios will likely survive- whereas Corys would get wasted ESPECIALLY in a 20G or under. Kribs are lovely pets though and very easy to care for. The water needs to be "wet"- thats it. PH, GH, KH, dont matter. Temp can be anywhere from 25 to 30. Eaaaaaasy fish.