How much area do the corner units take up?
Basically, this system encourages the growth of NitrAte-eating bacteria in an anaerobic environment? What does the NitrAte convert to?
the footprint in each corner is about the size of a medium sponge filter, although they are tall (approx 8"-10" high). They contain a reverse flow powerhead that pushes water through the undergravel plates and bypasses some of the water into slow flow de-nitrator block media. The media is contained within the towers themselves and the towers have three outlet ports built into the base. You place what look like pre-drilled riser tubes into the outlet ports which push the water out from the towers deeper along the undergravel plates for more even distribution under the plates themselves. It works pretty well in blowing all of the debris and mulm out of pea sized gravel up into the water column, where the power filter can get the gunk and remove it.
The de-nitrator blocks are designed to be a low oxygen zone, where anaerobic bacteria that eat NitrAte will colonize and grow. They convert NitrAte into nitrogen gas, which bubbles up and out of the system. There are similar denitrator blocks for saltwater setups and they're usually pretty massive to accomodate larger reef tanks. This is like that only on a much smaller scale, without all the muss and fuss of a jaubert plenum (had to clean, compaction) or a deep sand bed (compaction, anoxia issues).
So far, the unit is performing as advertised. The tests indicate zeros across the board for ammonia, NitrIte and NitrAte. It's a pretty great system for delaying the need for water changes. The potential drawbacks I see with the system are:
1) Power and filtration level: You have two powerheads and a 300 gph power filter going at all times. However, for what it does, the equipment you'd need to purchase separately on it's own would eat up just as much power if not more. The filtration level (for mechanical and the UGF) could potentially be underpowered or inappropreate in a larger setup such as a 55 gallon tank for some fish, such as fancy goldfish or fish that like to dig (ex: oscars). For these types of fish tanks, you might need to go with two power filters.
2) The filter plates: They were a bit of a pain to assemble and they didn't quite fit with a 20 gallon tall tank, so I had to do some adaptation to them. The filter plates themselves are 4" x 4" sqares with side guards and locking/support pegs. Since the unit is supposed to be adaptable to tanks from 20 to 55 gallons in standard rectangular sizes, this is a good way to do it from a designers standpoint, and you only have to do the installation once. Even so, it was a PITA.
3) The nutrients: The drawback here is twofold, a) you have an ongoing expense re-adding the nutrients to the tank week after week and b) it's a bit of a shotgun approach to adding essential trace elements and nutrients back to the tank. It's easy to maintain using the nutrients, but the big drawback that I see is that without an advanced testing center at your disposal, there's no way to accurately measure any one of the 70 trace elements/nutrients already present in the system, nor is there an accurate way to dose them back into the tank or removing them from the mix to prevent oversaturation. Add to that, the cost of re-ordering and re-using the nutrients. It's probably cheaper to do water changes in the long run.
The advantages:
1) Cleanliness: I can say without a doubt the tank is cleaner than it has ever been. The power filter/reverse flow UGF is a great combination for blowing all of the mulm, fish poo and uneaten food up into the water column for removal. The tank water looks absolutely pristine and clean and polished.
2) Works well: It works as advertised in our test tank. The equipment is made well and run silently. I didn't flush up the towers perfectly into the corners of the tank because of some reviews of rattling against the rear glass (easily solved with some sponge behind the tower). The power filter also runs quietly, unlike some tetra and whipser units.
All of the critical nitrogenous waste levels are at undetectable levels so far on my test kits. I'd love to put one of these on a small FOWLR or low fish density nano-reef and see how it does.
3) Perfect for the lazy: If water changes really are your achilles heel when it comes to fishkeeping, it's a great thing. It does truely delay the need for doing water changes. IMHO, it doesn't remove the need completely but it does dramatically reduce the need for doing them.
