Around 24-25 C is fine for most fish, unless you keep really warmth-loving species. Danios are active and sometimes a little nippy, so don't want to be kept with anything timid or trailing long, flowing fins. Also, they are surface fish, so ideally you should be aiming at another species that occupies the middle or bottom layers. See my post on cycling for danios- they need lots of swimming space and must be kept in schools.