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Unread 03/20/2019, 08:32 PM   #1
Chitownpw
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Denitrifying Reactor v water changing

Reefs.com posted a recent video on YouTube discussing custom built denitrifying reactors. Post-cycling of the reactor (i.e., after the relevant bacteria has adequately colonized the reactor chamber), tank water gets pulled into the reactor, methanol gets dosed into the water, this feeds the bacteria and the bacteria converts the nitrates in the water into gas that escapes. The concept is to pull so much of the tank water into the reactor each day to keep the nitrates at acceptable levels. At least, the above is what I took from the video.

Here are my questions: What are the benefits of using such a reactor over just running a constant water change system? If you pump X gallons through this a day to process out the nitrates, won’t a constant water change in the same amount effectively achieve the same result? Are there other benefits here over a constant water change system?


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Unread 03/20/2019, 09:00 PM   #2
bertoni
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The reactor could be cheaper than the water change system, and it likely would involve less manual effort. Mixing saltwater is very easy, though. Space for water storage might be an issue for some people.

The continuous water change would help keep all the parameters in line, and remove refractory organics, though, so it has some advantages.


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Unread 03/21/2019, 08:49 AM   #3
mcgyvr
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Remember.. Water changes are not just about nutrient reduction but also replenishing consumed elements and removing excess elements or helping to ensure they do not become elevated.


One can also basically achieve the exact same effect as a denitrifying reactor by simply carbon dosing right into the tank.. Methanol/Vinegar/Vodka/Sugar,etc... can be used as a bacterial energy/food source.


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Unread 03/21/2019, 05:05 PM   #4
dkeller_nc
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Yes, this is an extremely old method of nitrate reduction that was around when I started my first reef tank in 1990. It's essentially carbon dosing as McGyvr notes, with a twist. The bacteria responsible for reducing nitrate to nitrogen gas are obligate anaerobes (or at least facultative anaerobes) and use carbon sources as an electron donor to metabolize nitrate to nitrogen.

The idea of the reactor is efficiency; so long as the reactor doesn't have too much flow into it, it will be anoxic, and have a lot of surface area for the necessary bacteria to colonize. The same principle is a work with a sulfur denitrator reactor or a "coil" denitrator, though in the case of the sulfur denitrator the bacteria involved are different.

If you have a lot of porous live rock and/or a sandbed that's at least an inch thick, a denitrator reactor is probably superfluous - it's a heck of a lot easier to just dose the tank with a carbon source. But it might make sense for a minimally landscaped, bare bottom tank with a high fish load.


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