How long does a tank stay cycled without fish?

HI all

I would like to have an empty tank permanently cycled for emergencies (fish not getting on, fry found, sick fish), but once it is cycled (say, fishless), how long will it stay cycled if I never add fish in there?

Also, do I have to change the water once in a while in an empty tank and will that not compromise the cycle given the lack of ammonia sources in a fishless tank?

 

Are you saying you want a hospital tank?

 

You would have to "feed" the tank somehow to keep it cycled...

 

If you do not keep a constant source of ammonia going in the tank, the beneficial bacteria will start to die after a day or so, and you will have to cycle it all over again. There are a couple of approaches you could use...just put some flakes in daily to keep things going would be one option. Another would be to not worry about keeping it permanently cycled, but rather put some "excess" material in your main tank that you can move into the Q tank when you need to use it. For example, you could run a sponge filter in your main tank in addition to your normal filter, then just move the sponge over to the Q tank when it is needed. A similar approach would be to get a small internal filter to run in your main tank just to keep it seeded, then transfer it over to the Q as needed. This is what I have in mind: Another option would be to add some extra filter floss/foam to your normal filter, and transfer it to your Q tank filter when you need to use it.

 

Aaaah, that's a good idea (to keep a spare sponge in the main tank). Alternatively, sticking a bit of food in there everyday seems really easy too. Thanks, guys.

 

You're welcome!

 

If you would stick some food in the qt everyday could I still do a water change once a week on the tank? Or I guess I could get a betta and put it in there. Save it from those pet stores that put them in those small containers.

 

If you are using food to keep your bacteria alive in an uncycled tank, yes you should do periodic water changes with particular attention paid to vacuming out the uneaten food from the gravel.

 

Oooh, that's good advice, Sgould. Thanks for that.