Newbie Under-Gavel filter advice

Hi all, I'm new to aquariums and fishtanks and I'm thinking about using an under-gravel filter, after much consulting of the internet. When I went to my local stores(two of them) to check for pricing I got two very different responses to Under-Gravel filters. The first stores gave several success stories, talked about nice clear water, good plant growth and more along those lines. The second basically said, well we carry a few lines but with reluctance. The foremost critique being that an under-gravel filter carries away nutrients from the gravel and makes growing, or keeping alive, plants almost impossible. Since I want alot of plants and hopefully to keep them alive and growing. If under-gravel filters make life hard on plants I dont want one. On some sources on the internet however the opposite is claimed, and again in the first store. So I'm asking here: Are under-gravel filters good or bad? And if anyone has a good explanation as to why results seem to differ so much I would be very grateful! //Mattias F. Aldaron

If you want to have clear water and good water quality, they become high maintenance. Uneaten food and solid fish waste are pulled down into the gravel. Two things happen within the gravel - matting pockets of solid waste decompose and form hydrogen sulfide (smells like rotten eggs) which can be deadly to your fish, and/or, as the water flow pass' the solid waste, it dessolves and is pumped back into the tank as dissolved pollutants called DOCs (Dissolved Organic Compounds). The 'clear' water slowly starts to yellow, then becomes mucky, often resulting in foam being produced on the surface at the filters return outlets. Raised levels of DOCs; stress fish which weakens their defence system, ectoparasites such as flukes and protozoa thrive in high organic loaded water as does opportunistic bacteria, organic loaded water consumes a lot of oxygen and is inplicated in gill disease, etc... Of the three forms of pollution we deal with in aquaria, under gravel filters only deal with ammonia/nitrites - a cheap in-tank box or sponge filter does that! With UG filters, inorganic pollutants such as DOCs and the solid waste remain within the tank. Besides, gravel as a filter media has a (SSA) specific surface area) between 100 to 200 sq. meters per cubic meter. Plastic media 200 to 300, ceramic 250 to 350, matting 300 to 400, and foam (best) 400 to 500. The other two factors affecting filter media are; void space and cleanability - it's a lot easyer and faster to clean a foam sponge than the gravel above those under gravel filter plates. And then the under the plate has to be cleaned also. I found that the plant roots tend to clog UG filter plates, but the plants do grow well as does algae, after all, with an under gravel filter you will have an endless supply of plant nutrients (DOCs).... I would get a good bio-wheel filter, prefilter the intake and change at least 20% of the water once a week - that way your taking care of both your plants and fish needs.......... Frank

I would think that UGF's would eventually be problematic with a planted tank. From my understanding, UGFs eventually have to be removed and cleaned - making a complete mess out of a planted tank. Also plants with extensive root systems have the potential to clog UGF (probably an extreme case). I've only had a planted tank for a couple of years and run an Aqua Clear 300 on my 54 Gallon Corner tank. The only complaint I have is that tall thin plants have problems growing near the discharge of the filter - wave action breaks plant leaves - so I have a dead zone in the back.

I've never tried a canister filter - wondering if that might be the best of both worlds (comments anyone?).