# Cycling with existing filter



## fourtanks (May 4, 2010)

I just setup a new aquarium and installed a filter and media from an existing aquarium. I also added plants from the existing aquarium. Will my tank need to cycle or will the bacteria in the filter media start converting amonia to nitrite to nitrate immediatly?


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## flyin-lowe (Oct 3, 2009)

It depends on a few variables. How long was the filter in the old set up? Also how big was the original tank compared to the tank it is going in and what was the bio load of that tank compared to this one. Obviously you can't take a filter from lightly stocked 20g tank and put it into a 55 g heavily stocked tank and expect it to keep up. It will cycle a lot fast but maybe not instantly.
To give you an idea of a time line I recently set up a 120g tank. About a month before I set it up I took the filter media and sank it in the back of a 75g tank I had running. Once I set up the 120g I moved the filter media and immediately added enough ammonia to get it to about 2.0 ppm. After about 3 days it was processing ammonia but the nitrites were sky high and not coming down. I did about a 60% water change to drop the nitrites and after that it began making nitrates. Within seven days I could dose the ammonia up to 2.0 ppm and within 12 hours the ammonia and nitrites were back to 0.

All solid surfaces from your existing tank will have beneficial bacteria on it so if there is any decor or substrate you can move over as well it will help. I would suggest getting some ammonia and test it that way to be sure you have enough bacteria to handle the fish.


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