Right now I just have a fairly newish male "Petsmart" betta all by himself in a 1 gallon (yes I know it is too small - although way bigger than the stupid cup they sold him in!) and I was curious about bubble nests...what age do they start making them, is there a way to encourage it etc. He has a filter in the tank which is turned off now because too much water current on water surface - and his attitude changed when I shut off filter big time! He used to be a little shy but now if I go to check on him he gets very angry and has even done a dash against tank wall trying to get at me...I guess he likes the tank now! Just will hafta do major water changes with no filter but he looks way happier! Is his agressive behavior a good sign? His babies wouldn't be worth anything but I have never bred these guys before and experimenting would be safer with him...if I was successful I would go out and buy me some purty crowntails etc...they would sell easy I'm sure! Still haven't seen any in local petshops... so any advice from experienced folks would be muchly appreciated! 
