Happy betta = mean betta :(
So Cinder started making his first bubble nest after about two weeks in his new 10 gallon home. He is now extra protective of that side of the tank, which the Cory's also prefer and he has flared and actually attacked them briefly a couple of times. Now I think one of the Cory's had been bitten on one of his Ventral fins and has caused some fungus to grow there :( It is a white, fuzzy growth right at the base of the fin. Luckily he is eating normally and swimming normally, so I think I will dip him in some water with Methylene Blue for a few seconds and see if that helps.