I keep my filter off and only add the conditioner after the change. I leave it for about 10 mins then switch it back on.You put the conditioner in while it is filling. For example I did a water change to my 55g. While I'm filling the tank with water I'll dose the amount needed for 55g and let it fill. Been doing this for 6 months now.
Never had a spike since the bacs are in the canister.