Are they defensive strikes or feeding response strikes. I had a snake that would strike and kill his food but not eat it when temps were on the higher side. Did you say the fish tank is new to his enviroment, maybe the scent is freaking him out and and causing a combant mode? I am only guessing. Is there any chance there is a rodent in the area (wild maybe). Some of my snakes start striking as soon as I bring the rodents in the room. They smell them and will strike at the first heat signal that comes near them(me). Also if he isn't able to cool himself it maybe stressing him out big time. I just puchased a portable AC unit to keep my snake room from getting too hot. Temps are very important for health, feeding, breeding predictability. He needs a cool side in the lower to mid 80's.