How do I keep a mature filter alive in a fishless tank ?

its that simple Alan. Drop in a pinch of food just like you were
feeding the fish and then do a water change and gravel vac prior to
introducing the new fish.

Thanx. It made sense, but I like to be sure ;-)

Cleaver solution. I wonder if the food and no fish on a new tank
would work. I wrestled with this as I wanted to setup a quarantine
tank with no fish, but ready to use when needed. I ended up keeping
fish in the tank after a black molly dumped over 50 fry into the tank.
Wouldn't you know it, almost all lived.

Out of interest, this does work for fishless cycling. I have heard of
people trying it with success.

I have used ammonium bicarbonate for fishless cycling. This was fast and
easy. I guess any source of ammonia should work.

--
Alan Silver
PSG Fish Tanks - http://fish.alansilver.co.uk/

easy. I guess any source of ammonia should work.

thats right! no need to fuss with pure ammonia and getting the dose right -
just use fish food