The guy at petsmart told me if I used the bacteria-established cartridge filter from my existing tank in the filter of the new one for a few days, it would help set up the bacteria (this is all before adding livestock of course). Problem is that my existing cartridge filter doesn't fit in my new filter for the new tank. Would transferring one of the pieces of decor from my existing tank (that has growth on it) work the same way? Or not at all?

2 Answers 2


Hurray! Good advice from a pet store!

Yep, they are right. The easiest way to quickly get the cycle running in a new tank is to use existing bacteria that is already on the filter or surfaces on the tank. Unless there's any health concerns with your original tank, there's no reason not to transfer them across. After all, you did all the hard work cultivating the bacteria the first time, why not make it a little easier this time, eh?

Additional Notes:

  • You say that the cartridge doesn't fit in the other tank but if you can get it to sit in a place of reasonable flow within the new tank, there's no reason that you can't leave it outside the filtration mechanism.
  • Remember, you'll still want to be doing regular water parameter tests in the early days to ensure that the bacteria has established itself.
  • You need to 'feed' your bacteria - They'll need some ammonia to chew on while they're getting established. You could chuck a flake or two in which will decompose and create ammonia.
  • As @trondHansen points out, the bigger the decoration! You could even bring some substrate (gravel / sand) if you have some easily to hand.
  • Maybe it was a nice local pet store, instead of petsmart or petco...
    – Ginge
    Jul 16, 2019 at 16:25

Yes, moving some of your decorations to the new tank will help seed the new tank.

You need to use one that have as large a surface area as possible. The two types of bacteria are Nitrobacter and Nitrosomonas, they live on every surface of your tank.

Nitrobacter is a genus of aerobic bacteria and Nitrosomonas is a genus of anaerobic bacteria.

Nitrosomonas live directly on the surfaces in your tank. They do not need oxygen and on top of them Nitrobacter live - they use oxygen and protect the underlying bacteria from the oxygen in the water (this is why it takes time to cycle a tank, the two bacteria types are dependent on each other).

As long as the decorations do not dry out the bacteria will survive. But they still need time to spread and multiply in your new tank to be able to handle the waste.

Remember to use dechlorinator before you add the decorations with the bacteria in your new tank.

If you use lava rock or zeolite (for fish tanks) as decoration or in your filter, you will always have a supply of bacteria you can use to start a new tank.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.