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Anoxic filter. Is it worth it?


Daviscoast
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Hi, I was recently going through YouTube and found this interesting topic on a new filter I never heard of that got rid of nitrates almost all together after matururing. The science is proven but is it worth getting one? Also if you don't know what an anoxic filter is, it is basically a low oxygen environment that allows bacteria to strip nitrates if oxegeon and leaves nitrogen which transfers into the air. What are your thoughts?

 

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I don’t know much about them but I have read about them. I would be concerned it would outcompete my plants for the nutrients it needs. I’m also a firm believer my entire life there is benefit to FRESH water not just clean water. There are tons of micro nutrients etc we don’t test for that are depleted and tons of bacteria that exponentially increase.  Regular water changes to me are essential (I know many folks who are successful with no water changes) so in my world it becomes an unnecessary expense. The only time any of my tanks struggle with nitrates (my source water comes out average 20ppm). Is when it is newer.  After it seasons it balances out again and that would be about the time it starts working making that expense unneeded. If you try it I would be very curious and enjoy reading about your progress. I love learning new things even if it is not something I would do. 😁

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"The science is proven..." Eh, as a rule very little in science is truly proven when it comes to aquariums. Our aquariums have a gazillion (give or take a few) variables and what works in a lab, or one tank, may fail completely in another. I like the idea of anoxic filtration and it sounds good in concept, but you'd have to reoxygenate the water going back into the tank (which isn't too hard.) There's also the problem of methane and hydrogen sulfide being created and released by an anoxic filter. (More challenging to prevent/deal with.) It's something I've played with a tiny little bit, but never found truly worthwhile.

I'm not sure a fine sponge filter  that's seldom cleaned doesn't becomes an anoxic filter over time. Keeping two sponge filters in a tank and never cleaning one may be the easy way to achieve anoxic filtration. Sponge filters hold a lot of bacteria. A clogged, fine pore sponge filter would have minimal water flow through it. Kind of the perfect environment for anoxic filtration. Maybe not even connecting one to an airline and just having it sitting there would make it an anoxic filter? Spongefilters are good media for aerobic  bacteria so a clogged one with minimal wate flow/aeration might just be ideal for anoxic filtration. Or so my warped mind thinks. (It's also a good excuse not to clean my sponge filters.)

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We have talked about this topic quite extensively here. To summarize anaerobic bacteria filtration would have to exist outside of the display as fish could potentially release the toxic gases associated with the process. The other concerns are that of space and efficiency.

 

Having that been said I am introducing a "hybrid" system once my mangroves grow out. While I expect the mangroves to do most of the nitrate removal as plants do best I will also have aerobic bacteria in an aerobic refugium cleaning up whatever is left. Mangroves prefer anoxic mud as their growing medium and use spikes to get oxygen to their roots.

Edited by Biotope Biologist
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The reason I wanted to try this is because I wanted to set up a biotope. With Herman blue rams, bristlenose, corys, tetras and some other sort of chiclid like a angel or discuss. I want it to be all natural and observe the rams claim territory and breed and the Cory eggs being scattered all across the glass with the tetras breeding in the Java moss. It is my dream aquarium and to make it as natural as possible I wanted to experiment with anoxic filtration to expand the overall process of the cycle. Anyone else who wants to do the same? 

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On 9/28/2021 at 9:57 AM, gardenman said:

"The science is proven..." Eh, as a rule very little in science is truly proven when it comes to aquariums. Our aquariums have a gazillion (give or take a few) variables and what works in a lab, or one tank, may fail completely in another. I like the idea of anoxic filtration and it sounds good in concept, but you'd have to reoxygenate the water going back into the tank (which isn't too hard.) There's also the problem of methane and hydrogen sulfide being created and released by an anoxic filter. (More challenging to prevent/deal with.) It's something I've played with a tiny little bit, but never found truly worthwhile.

I'm not sure a fine sponge filter  that's seldom cleaned doesn't becomes an anoxic filter over time. Keeping two sponge filters in a tank and never cleaning one may be the easy way to achieve anoxic filtration. Sponge filters hold a lot of bacteria. A clogged, fine pore sponge filter would have minimal water flow through it. Kind of the perfect environment for anoxic filtration. Maybe not even connecting one to an airline and just having it sitting there would make it an anoxic filter? Spongefilters are good media for aerobic  bacteria so a clogged one with minimal wate flow/aeration might just be ideal for anoxic filtration. Or so my warped mind thinks. (It's also a good excuse not to clean my sponge filters.)

I never thought of fine sponge filters that way, but it would have to be pretty clogged to work that way.  If so, I’ve been there, done that without even trying!  😆 

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On 9/28/2021 at 5:43 PM, Odd Duck said:

I never thought of fine sponge filters that way, but it would have to be pretty clogged to work that way.  If so, I’ve been there, done that without even trying!  😆 

Most of us probably have been there and done that. It does make sense though. One of the drawbacks of the fine sponge filters is they do clog easily. A clogged fine sponge filter sitting in a tank might just become an anoxic filter. (At least in part. The outer surface would still be doing aerobic work due to the oxygen in the water, but the deeper internal parts might just be anoxic.) 

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On 9/28/2021 at 2:35 AM, Daviscoast said:

Hi, I was recently going through YouTube and found this interesting topic on a new filter I never heard of that got rid of nitrates almost all together after matururing. The science is proven but is it worth getting one? Also if you don't know what an anoxic filter is, it is basically a low oxygen environment that allows bacteria to strip nitrates if oxegeon and leaves nitrogen which transfers into the air. What are your thoughts?

 

This was the premise to explain the success of the German deep substrate tanks.

Anoxic bacteria takes care of fish waste/nitrates. Plants take care of fish waste ammonia and ammonium, as those are actually easier for plants to utilize than nitrates.

Roots from plants, Malaysian trumpet snails, and black worms keep the top 1.5" to 2" of substrate well turned over and helps the substrate capture the mulm. The anoxic layer of bacteria is generally 3" to 4" deep, and will be very dark, almost black if you have white sand.

If I remember correctly, there is a chapter dedicated to anoxic bacteria in Walstad's "Treatise".... or it was in my German fish keeping book.

I'm not getting out of bed to go look right now 🤭

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I don't have any experience or opinions about anoxic filtration, it's an exciting idea to me but I've never quite understood how it could practically be achieved. 

In order for it to work presumably you have to get the water containing the nitrates to the denitrifying bacteria right? How is this possible without also introducing oxygen? 

I suppose theoretically a system could be devised where the water travels through the filter/sump and the oxygen gets used up by the nitrifying bacteria before it reaches the denitrifying bacteria and then gets oxygenated again as it gets pumped back into the tank but it would take a lot of "dialling in" with flow and surface area etc surely? If I understand it correctly if too much oxygenated water reaches the denitrifying bacteria it would kill it off and you would need to re-establish it all again from the start? Just seems like too many variables to be worth attempting it but I'm probably missing something.

I certainly don't understand how deep sand beds etc work, in my head logically either the water is moving through it which means too much oxygen or not moving through it which means the nitrates won't reach it to be filtered out? Or at least if the water is moving through it slow enough to become deoxygenated it would also be too slow to filter out nitrates very quickly. 

Is there another way of removing oxygen that I'm missing? Or like can nitrates travel through the substrate independent of the water somehow? 

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On 9/28/2021 at 11:46 PM, KentFishFanUK said:

don't understand how deep sand beds etc work, in my head logically either the water is moving through it which means too much oxygen or not moving through it which means the nitrates won't reach it to be filtered out? Or at least if the water is moving through it slow enough to become deoxygenated it would also be too slow to filter out nitrates very quickly. 

Is there another way of removing oxygen that I'm missing? Or like can nitrates travel through the substrate independent of the water somehow? 

I learned the hard way in my Walstad tank, you need plenty of MTS, black worms, and plant roots, or you can get hydrogen sulfate .... not the end of the world....

But I lost about 75% of one of my stem plants...  😕  

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On 9/29/2021 at 4:38 PM, Diving Aquarist said:

The method researched by Dr. Novak requires an under gravel filter that is connected to an air pump. To create the low oxigen concentration in the lower parts, the amount of water displaced by that filter is low. Slow moving water is the key. A 'BCB' basket is another option. This also relies on slow moving water.

Another option is to just let diffusion do its thing, but that is a very slow process.

I don't see letting worms etc constantly turning over the soil create anoxic conditions. To me it looks like it is a way to oxigenate the soil.

The problem with the sponge filter theory, is that the filters get clogged with fish waste. This will start to rot and release ammonia etc into the water. If it is really clogged, you create anaerobic conditions, and you don't want that. The Biohome filter media is somewhat that idea, but the intention seems to be to create anaerobic conditions. I can't speak to the effectiveness of that media, but it is pretty expensive.

Even with the slow moving water I can't quite wrap my head around it, is the oxygen supposed to be depleted by the denitrifying bacteria before it reaches the anoxic bacteria? That sort of makes sense, except that in order for the oxygen to be depleted you'd need enough bacteria consuming it but in order to do that it would need enough ammonia/nitrites to use up all the oxygen wouldn't it? Which then makes even more nitrates so it would almost seem counter productive.

I suppose given time and very stable conditions, enough surface area for the denitrifying bacteria and then enough surface area for the anoxic bacteria it would all reach a balance but doesn't sound simple at all, especially when compared with plants that could essentially do the same thing. 

Maybe I just need to read this Dr. Novak person haha

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  • 6 months later...

In my opinion it's definitely worth it, my tanks are doing better than ever, by far.

All you need is a UGF with about 3 inches of SafeTSorb and some liquid iron fertilizer. 

I run the uplift tube to the surface to monitor the flow. I thought it would be best to have the uplift tube next to an air stone to reoxygenate the water from the plenum, but maybe it's not. The one tank I setup that way still has some nitrates, that tank has 4 Mexican dwarf crayfish so maybe their waste is just different from the fish somehow.

I have slow flow plenums in three tanks, a 20 long, standard 10 gallon, and a 5.5 gallon. The 20 and 5.5 are at zero nitrates and the 10 is around 10ppm nitrates. They are all moderately planted and thriving.

The 5.5 gallon has 6 green corys, 4 guppies (one is a baby), and 2 mystery snails,  so it's a bit overstocked, but they are looking and acting better than when they were in my conventionally setup 29 gallon tall tank.

 

Another plus is that it's very cheap. I spent $30 for all three tanks with enough left over for another small one.

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