Umm ... 8 dwarfs in a 20 Gallon?! Thats waaay too much, you will Definatly get too much chasing/fighting in that then. Personally, I'd say dont keep more than 4/5 dwarfs in a 20 Gallon. Besides that, I think pretty much all info has been given already.bunjiweb said:In a 20G tank you could get up to 5 - 8 dwarf puffers in a 20G with adequate filtration.