Q: I'm about to buy a new tank, 2ft x 1ft. I'm going to get the eheim 150 power filter for it...or Aquaclear 150..both much the same. But I wondering if I should get an undergravel filter for it as well? Does it serve an extra purpose or is there not really any need?

A:I am not a big fan of UG filters and have not used them for years, Here's why (remember this is opinion).The UG filter is a bacterial filter that utilizes a huge surface area ( the gravel bed ) and the gravel as the medium for the bacteria to grow on. this is great when everything is new and clean and the tank is bare. The lift tubes create a current that causes the water to flow through the the gravel, under the plates and out again. This current brings the oxygen and food to the bacteria. the good bacteria are aerobic and need oxygen to live. Now over time the waste accumulates on the bottom of the plates and sections of the gravel become blocked. In these areas the water has no oxygen and the anaerobic bacteria start to grow. Anaerobic bacteria respirate deadly gasses that form bubbles in the bed and under the decorations. Anytime they are disturbed they release into the water and can harm the fish. Over time the entire gravel bed will break down and no longer be effective. Once this occurs you must completely break down the tank clean the gravel, under the plates and start all over again. not something I want to do!. Now a 5 gallon is not so large as to be too much of a problem, but just imagine a larger 4 foot 55 gallon, not a pleasant thought. The UGs do work and do it well but in my opinion the "future" maintenance issue far outweighs the benefits.

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