Actually swish it around. The problem with changing your cartridge is stalling the ammonia cycle.
Ummmmm... So your saying that I, should, rinse, my old dirty cartridge, in the water that it got dirty from...
I never clean my tank completely anymore and I don't have a bio-wheel or bio-ball filter, so do I still need to swish my cartridges.
The cats watch this tank and bichir-girl feeds it... I pay very little attention to it unless I'm told there is a problem. In looking at it today, the fish are bigger than I thought they were AND I discovered a 6th goldfish in the tank. Bichir-girl has subsequently confessed to adding another fish and is mortified I posted pictures of her cat's tank without cleaning the algae on the glass. So yes, I think we're about due for a tank upgrade or a fish reduction. Let the fight with Bichir-girl commence! LOL