Q & A - Undergravel Filtration

I would like to bring up the concept of undergravel filtration. I am not a fan. I do, however, think they can be beneficial in a non-planted, rocky type African tank when it is used as a reverse filter - water is forced up through the gravel from beneath. This keeps the substrate clear of debris, lifting anything resting on it into the water column to be picked up by the main filter. This is not practical in a planted tank, where you would not want to disturb root growth and there are too many obstructions in the tank to make it function properly.


For the same reason I would not use a UGF in a planted tank. The roots need to be able to grow in the substrate, and they'll clog up the filter plate beneath the gravel. Then there is the unavoidable situation of detritus collecting beneath the filter plates, which at some point needs to be addressed, and generally requires a complete tear-down of the tank to accomplish. That will almost always involve re-cycling of the tank, though not always.


There are so many filtration options these days, and alternatives to gravel as well. Don't tell anyone, as many would argue until they are blue that I am wrong (I very well may be), but it is my secret belief that the only purpose of typical aquarium gravel is to aid in the use of an undergravel filter, where the coarse texture keeps most large debris from falling down to the filter plates, but at the same time allows good movement of oxygenated water through the gravel, building bacterial colonies. Now that those filters have gone out of style, so to speak, everyone is still clinging to the use of gravel.


It is coarse and allows much too much debris to collect in it, no matter how diligent you are with your gravel vac, and it is a poor plant substrate (not horrible, just poor). Finer gravels and sands are what I prefer, though it has been only in the past 5 years or less that I have come to this conclusion. I have abandoned gravel to be used in the tops of my potted terrestrial houseplants - it covers the ugly dirt just great!