DIY Denitrator Idea

[wow_it_esploded]

A good sponge should list it's density, it might be PPI (parts per inch i assume) or in pore size (micron). If you're looking for like, micron sized filtering, you might want to consider a cartridge filter of some sort, like one of those "big blue" whole house filters.

 

[sc2dave]

Creating a completely anaerobic denitrator is going to be really dangerous.

How Dangerous?

 

[ToolMan78]

Sounds great, but I don't have the experience to know what kind of area I would need to provide for an overstocked system (which is basically what any oscar-dedicated tank is...). I want a small and compact system that I can hide away somewhere. I'm considering a string of sponges as the mechanical filter intake for a 1300 GPH pump, which would push water through a Pond Matrix bio filter. I just can't seem to figure out how thorough sponges are. If they're 200 micron or something large like that, I'm not interested... but how do you figure that out? I have Hydro sponges now, but I never saw them as mechanical filters before... but they certainly keep my water clear and need to be replaced now and then. I love them.

Don't think your going to get small compact system to handle the nitrate that a group of grown oscars produces. I looked at what Pond Matrix is and although they state that it also performs denitrification, you need to take this with a grain of salt. It can offer a little denitrification due to it's size and porosity. Water that infiltrates to the center passes an aerobic layer first that consumes the oxygen and as it reaches the deeper zones of the media denitrification can take place. But you need to realize that the diffusion of nitrate to the anaerobic zone in the media is extremely slow. Also the anaerobic zone is only a small portion of the media. So you would need huge amounts to put a dent in the nitrate that a oscar produces. I didn't do the math, but think of a second tank of equall size to your oscar's filled with Pond Matrix. That might be enough to space your water changes out significantly.
Dedicated denitrification filters are complex in their operation. First of as was already stated, you need to maintain the the Redox levels where they need to be to encourage denitrification and not creation of hydrogen sulfide. Also denitrification requires food for the anaerobic baceria that do it. That needs to be in the form of dissolved organic carbon. That could be a variety of things: sugar, vinegar, alcohol, etc. For the small amount of denitrification that goes on in the Pond Matrix nothing needs to be added as the normal breakdown of fish food and dead organisms provide a certain amount continuously.
In short, denitrification filters are not something your just gonna build without a lot of research. There have been people who have built working denitrification filters. The ones I'm familiar with were neither small nor low maintenance.

 

[josolanes]

fwiw fairly heavily planted tanks or tanks with column feeder plants such as floaters work very well with removing nitrates especially given ample light and potassium and phosphate fertilizers (allowing the plants to use more of the free nitrates in the tank to fulfill the 3 macro ferts - nitrogen, potassium, phosphate)

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