Sory i dont know how to spell it but i came home today and the co2 levels were high 3 fish amybe 4 dead(the catfish) the biggger fish are strugging upside down.I put the pump on took out the co2 diffuser and a pro aqua plant bag i put in as fertiliser in case that was causing it.IS this aesphyxiation?WHat else should i do?