# Where do bacteria live?



## psyber (Jan 7, 2009)

Quick question, I hope.

Where in the tank do most of the bacteria inside a tank live? In the substrate (like most packages of aquarium gravel and such imply) or the filter media? Does adding substrate increase the amount of beneficial bacteria in a tank?


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## lotsofish (Feb 28, 2008)

Mainly in the filter media although they are throughout the tank. Adding substrate may increase beneficial bacteria but it can also increase the bad anaerobic bacteria that can release harmful toxins. The good bacteria need oxygen so the aeration of a good filter system grow the best bacteria cultures. That is why the bio-wheels have become so popular but many other filters do a fine job too.


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## prov356 (Sep 20, 2006)

Good bacteria live anywhere there's a surface they can adhere to that has a flow of oxygenated water. 
Rocks, decor, top layer of substrate, filter media, filter hoses, tank walls, etc. Most usually are in the 
filter media because it has a good flow of water and the most surface area for bacteria to colonize. This 
can vary, of course, depending on filter maintenance. If allowed to get gunked up and flow is reduced, 
then these numbers can drop. I think age of aquarium makes a difference. In a well aged aquarium, 
there's probably much more throughout the tank than a new setup. That's why it's important to go easy 
with filter cleaning in the early life of a tank. Later, you should still be careful, but more room for error.

HTH


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## remarkosmoc (Oct 19, 2005)

As prov said every surface of the tank. They will prefer the locations that have better circulation to bring them nutrients and oxygen. A misconception is that every surface of the tank and filters will be completely covered. The bacteria will grow and divide and spread until they reach and equiliberium with the ammonia produced. A tank with a steady level of fish producing a steady level of waste will have a near constant amount of bacteria, which is the maximum that will survive based on that input of nutrieints. This is why no matter how established your tank is you should always add new fish slowly or at least carefully monitor water parameters after increasing the bioload. Tank size and adequate biomedia are important in this regard. If you have adequate biomedia such that there is room for expansion, the bacteria will quickly spread to devour the inreased bioload but if your capability is near max they will not.


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