Would those people be pet shop workers? Anywase that is just my suggestion having had a 10g, and danios, I would personally never put them under a group of 8 and in a 20 long.. I find this is a perfect example of why 1inch a gallon is not a good rule.. 5they don't have enough room to swim around in a 10g.. Maybe someone else would have different info, but I have seen this topic before and most people (all I believe) believe like me.. Anywase good luck!