How Much Of The Beneficial Bacteria Is In The Filter Biomedia? - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 4 Old 07-18-2012, 06:54 AM Thread Starter
How Much Of The Beneficial Bacteria Is In The Filter Biomedia?

I've been wondering about this issue, just as something to think about. The question really is, knowing that beneficial bacteria bind to every surface of the tank, and knowing that there is a lot of surface area in the biomedia in the filter, what percentage of the total of the beneficial bacteria resides in the filter biomedia?

I guess this would depend on the tank size, with a larger tank with a filter of the same size (for the sake of argument) bearing less of a percentage of beneficial bacteria. I have an Aquaclear 30 HOB on a 10 gallon tank.

My uneducated guess is, especially in a moderately to heavily planted tank, that most of the bacteria are in the tank, especially as tank size goes up. A conclusion would be that water circulation is very important. This would be a factor in where in the tank bacteria can do their work and participate in the Nitrogen cycle.

One more thing - plants use nitrogen in ammonia, nitrite, and nitrate, competing with the beneficial bacteria - outcompeting I would say. I believe that plants get the nitrogen first and hold onto it, then the bacteria get the rest, if any, eventually showing up as the end product of the Nitrogen cycle, Nitrate.

Back to the original question - where do you think the majority of beneficial bacteria is, in the filter or in the tank?

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post #2 of 4 Old 07-18-2012, 07:21 AM
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Well, I think it's a matter of surface area for the most part. That includes all of the little nooks and crannies in the filter media and the substrate and objects in the tank. I would think that the tank would contain the majority of the beneficial bacteria; however, the amount in the filter media is still substantial.

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post #3 of 4 Old 07-18-2012, 10:37 AM
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In the filter, since it force feeds the bacteria. The majority of the bacteria will live where ever the concentration of food is the highest. That's why you can move the entire filter to a new tank and have an instant cycle, and why swapping out a new filter (and media) for an established one wrecks everything.

But as you eluded to, there are many variable to consider so it is not a one size fits all situation.

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post #4 of 4 Old 07-18-2012, 02:08 PM
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There will always be more bacteria in the substrate than in the filter.

Having said that, one has to determine what bacteria you might be referring to. "Beneficial" applies to all bacteria, whether autotrophic or heterotrophic, aerobic or anaerobic. My article on bacteria touches on all this.

If you were meaning solely nitrifying bacteria, namely Nitrosomonas and Nitrospira species, you would likely find fewer in the filter than elsewhere. Aside from live plants keeping this bacteria lower in numbers, the type of filter and frequency of cleaning impact numbers. The heterotrophic bacteria multiply considerably faster and will usually overwhelm the autotrophic nitrifying bacteria.


Byron Hosking, BMus, MA
Vancouver, BC, Canada

The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian. [unknown source]

Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]
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