A little bit ago, I did an experiment running this company's product, which claimed to eliminate the need for water changes. I ran the product, as stated, for a month, and I have since continued running parts of it for well over a month.
I have to say that I was very surprised to find that the system worked. In an overstocked tank, the system kept the nitrates at around 5ppm, once the tank cycled.
I do have a problem with the way the company claims that its product instantly cycles the tank. It actually uses what I call "smoke and mirrors" to give you an invisible cycle. Chemical filtration pulls most of the nitrogen out of the water before it can make your fish sick. It worked, but I would have preferred to cycle the tank a different way and add fish after it was cycled.
The product is also pricey. $60 for the main equipment for up to 20g, $100 for the main equipment for up to 120g. The main equipment comes in the form of two towers that run reverse under gravel filters. The towers supposedly have controlled anaerobic zones in them that support denitrifying bacteria (which turn nitrates into gaseous nitrogen.) The
UGF plates are customizable, and can be made to fit nearly any flat-bottomed aquarium, even an oddly-shaped one.
Hi-Q also makes a good
HOB filter. I would rate it as a bit better than a Whisper filter. It uses chemical media (I have since jury-rigged chemical-free media) and bio-balls.
Lastly, there is the BioMagic and VitaMagic. VitaMagic is basically a combination of StressCoat and Vita-Chem. The BioMagic is a bacteria that is supposedly engineered to turn nitrates into gaseous nitrogen. BioMagic doesn't seem to work without the towers, though I am continuing to test this, just to be sure.
My suggestion, if you want to plunk down the money for any part of this system:
Get the towers/UGF, install them. Get whatever HOB or other filtration you want to use.
Cycle your tank normally, adding BioMagic as instructed (I'm not positive that the stuff is needed, but I'm also not positive that it's not. I can tell you that it has not been harmful to my tank, and it's a minor expenditure compared to the towers themselves).
Once the tank is cycled, add fish.
Keep an eye on water quality as normal, and do water changes if any parameters are out of whack.