My apologies. Usually, I go to reliable websites where the interface looks orderly and attractive, you'll find articles on those websites, which are not too broad in spectrum. As for regards with the no. in one tank, you'll probably need to have some experience and make some guess. Chubbies are not terribly active, but they are extremely good escape artists, I have had 10 of them escape into my backyard(they're native here). Today, we still hear the chubbies mocking me with loud cow like noises.

Oh yes, I must say that they can dry out underground, so watch out in keeping the substrate moist.