Hi My cycling seems to have come to a halt: for over a week the ammonia has stayed at 0.25, Nitrites 0 and nitrate has crept up to 0.25 I could exchange some water and this may bring ammonia down to zero ? Also I am expecting delivery of a canister filter hopefully to eventually replace the three interpet internal filters.. How shall I add this into the system. I could remove the sponge from one of the interpet cassettes and some how put into the canister. Should I leave the remaining two interpet in the tank. or do I have to start over the cycling with the can'