# diy aquarium water recycler



## djsuspence (Jan 15, 2014)

hello everyone, 
So I've been working on a water recycler which will take old aquarium water and filter it through several chambers, which will make it useable again as new, fresh aquarium water. I'm moving to a place where water regulations are highly controlled so this is a good way to help eliminate over usage of water. basically *** figured out how to remove all of the negative agents in old aquarium water but what I'm having trouble with is the removal of nitrates. I've thought of the idea of using plants, which will remove some nitrates but not all, I'm just trying to get the water as pure as i can. As per the nitrogen cycle: bacteria and fungi break down uneaten food, dead organisms, and fish, plant, and invertebrate waste into ammonia. Aerobic bacteria, which need oxygen to survive, then break down ammonia into nitrite, and nitrite into nitrate. Than there is also another bacteria set that converts nitrate into nitrogen gas, which is then released at the water's surface and absorbed into the air. This is the natural e-nitrification process I'm trying to achieve.

The problem I'm having with complete nitrification, however, is that the process relies on special bacteria to convert nitrate into free nitrogen. These bacteria require low-oxygenated, stagnant water to survive. i was just wondering if anyone has any specific knowledge or can point me in the right direction. Would filtering the water completely and than storing the water in a container to turn the nitrate into nitrogen work?? Thank you in advance!!


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## BillD (May 17, 2005)

There are denitrators available that will do that. A natural way is to use a plenum, which is an open space beneath the substrate. The space becomes inhabited with the anaerobic bacteria that convert nitrate to nitrogen gas. What you need is a space about the height of a double thickness of egg crate lighting grate, covered with window screen. Above this you want about 2 inches of inert gravel of 1/8" size. Water will move slowly from above to below the plate as the system strives for equilibrium. With such slow water flow, the area below the plate stays anoxic. We had a speaker come to our club a number of years ago that was bringing just such a product to market. It seems to have not happened, but is pretty much as described above. Plenums have been used in marine systems in the past, but, I don't know if they are still popular. Do a search for "Plenums in aquaria" and you will find numerous articles.
My concern would be that while you may remove all nitrogenous wastes from the water, that there would still be other metabolic wastes that would build up over time.


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## djsuspence (Jan 15, 2014)

First off, I would like to say thank you. This is exactly the feed back I was looking for.

I will certainly dot research. I'm currently in contact with a marine biologist professor at my local university but this is definitely a step in the right direction. That you for your shared knowledge.


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## Fishnut71 (Dec 7, 2014)

What I can't seem to figure out about this plenum method is: how do you create an environment that needs to be O2 poor to exist and at the same time expose it to O2 rich water in order to introduce nitrate?

If this method was successful, I strongly believe many in the hobby would be utilizing it....at least, on the freshwater side of it.

I've read a number of accounts of fish keepers who incorporates plant hydroponic systems into their freshwater fish system with very few annual water changes and attest to being highly successful. I myself use a small scale pothos set-up and have been impressed with the nitrate reduction. So, I believe a larger enough scale pothos set-up can bring nitrate down to zero.

Furthermore, I remember, a while back, reading about sewage treatment facilities that utilizes water based plants to "purify" water. Enough so, that it is safe once again for human consumption.

With the water shortage crisis in Cali, this may be your best option in cutting down, way down, on water changes


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## djsuspence (Jan 15, 2014)

fishnut71 thats a really good breakdown. thanks for the info


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## BillD (May 17, 2005)

Fishnut71 said:


> What I can't seem to figure out about this plenum method is: how do you create an environment that needs to be O2 poor to exist and at the same time expose it to O2 rich water in order to introduce nitrate?


Water moves from the area below the plenum very slowly as the system tries to gain equilibrium. The layer of gravel is the barrier that allows this to happen. It needs to be a minimum depth to work. If there isn't a deep enough layer the water would move too quickly and you would lose the anoxic conditions in the plenum.


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