# both aerobic (nitrifying) and anaerobic (de-nitrifying)



## Ape-Fish (Jul 1, 2006)

Are there any filters for fresh water tanks that uses both aerobic (nitrifying) and anaerobic (de-nitrifying) bacterial functions? opcorn: I know bio-balls do only aerobic (nitrifying) bacterial functions, and then you have to remove the nitrate with the water changes. I hear there are bio-media for salt water tanks with deep pores that house both aerobic (nitrifying) and anaerobic (de-nitrifying) bacteria that remove the nitrates...


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## dreday (Oct 12, 2007)

i have heard of nitrate reactors that are supposed to keep nitrate to a minimum. not sure how they work though.


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## Guest (Oct 20, 2008)

From what I've heard they actually convert Nitrate back into Nitrite...not sure if it's true though.

Either way the only effective way to keep it down is to have the tank well planted...otherwise the only way is by water changes...


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## prov356 (Sep 20, 2006)

> From what I've heard they actually convert Nitrate back into Nitrite...not sure if it's true though.


It is true. That is one of the intermediary processes in de-nitrification.

See http://en.wikipedia.org/wiki/Denitrification

To try to run the de-nitrification process in a tank is always a risky thing because you need to be sure
that you allow for the release of any end or intermediary products safely.

Reef tanks nowadays typically don't even run biomedia of any kind. Nitrification happens within the 
live rock. De-nitrification also since there are usually areas deep within it where there's little oxygen 
flow. The other typical method is what's called a 'deep sand bed'.



> I hear there are bio-media for salt water tanks with deep pores that house both aerobic (nitrifying) and anaerobic (de-nitrifying) bacteria that remove the nitrates...


I've seen some biomedia claim it'll harbor both aerobic and anaerobic bacteria, but I'm always 
skeptical of those claims. The idea is that there are deep enough pores for a 'no oxygen' area like 
you'd find in live rock within a reef tank. If true, then I'm not sure why that would only work in a salt 
water tank. Theoretically, it should then work in fresh water too. But again, I doubt that it does much, 
if anything, to reduce nitrates. Just more marketing hype.


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## Fishbulb2 (Sep 23, 2008)

You can look into seachem's denitrate. It works as prov356 has described. Aerobic bacteria grow on the outside and result in anaerobic conditions inside the media. The draw back is that this requires a slow flow rate of only 50 gallons per hour or less. You will not get this in most power filters. If you have a phosban reactor you can use that to provide the adequate flow rate to denitrate.


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## Ape-Fish (Jul 1, 2006)

OK thanks guys! So... if it just changes the Nitrates back into nitrites, why does it help? :-?


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## prov356 (Sep 20, 2006)

> if it just changes the Nitrates back into nitrites, why does it help?


That's just one step in the process of converting it to a gas that is eventually released from the system 
(hopefully harmlessly). The risk with these systems is that something will get released into the main 
system that you don't want. It can work if done correctly though. It's just not common in the freshwater 
world.


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## AquaTester55 (Aug 16, 2006)

> It is true. That is one of the intermediary processes in de-nitrification


No its not. Denitrators break down the nitrates into nitrogen gas which is released into the air later on. They do not turn nitrates back into nitrites.



> That's just one step in the process of converting it to a gas that is eventually released from the system
> (hopefully harmlessly). The risk with these systems is that something will get released into the main
> system that you don't want. It can work if done correctly though. It's just not common in the freshwater
> world.


There are nitrate filters which use sulfer pellets to remove the nitrate. This can leach into the water giving it a sulfer smell. Other filters there won't be anything that will leach into the main water other than what you put into the filter to feed the anaerobic bacteria.

Anaerobic filters need to have an oxygen depleted environment with an extermly slow flow rate. This is the exact opposite of aerobic bacteria filter which needs a high oxygen environment.


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## prov356 (Sep 20, 2006)

> No its not. Denitrators break down the nitrates into nitrogen gas which is released into the air later on. They do not turn nitrates back into nitrites.


See http://en.wikipedia.org/wiki/Denitrification

From the site



> Denitrification generally proceeds through some combination of the following intermediate forms:
> 
> NO3- → NO2- → NO → N2O → N2 gas


It's very well documented all over the place. Google it. Do some research, them come talk to me.


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## AquaTester55 (Aug 16, 2006)

It produces nitrite of your flow is to fast which will not allow the bacteria to break down the nitrate molecules completly which yes could introduce nitrite into your aquarium.

I am pointing out the fact that is does not convert nitrate into nitrite and thats the end of the cycle. That is being said.

With a properly setup anaerobic bacteri filter you should have zero nitrite and very little nitrate if any come out of the filter.


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## prov356 (Sep 20, 2006)

> That is one of the *intermediary *processes in de-nitrification.


Then, we're in agreement. :thumb: I said *intermediary *step in the process of converting nitrate 
to nitrogen gas. I didn't say it was the end of the process.


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## BillD (May 17, 2005)

Installing a plenum beneath the substrate can remove nitrates. However, removing nitrates does not remove the need to do water changes. There are many other biological wastes that we don't test for that should be removed, and the best way is partial water changes. A high nitrate level, which may not be that harmful in itself, tells you that you need to change water.


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