newby sam

If I purchase a 55 gallon tank and use a simple filter that comes with it along with an undergravel filter, is that sufficent? Why does everyone say not to use an undergravel filter?

sgould

http://www.bestfish.com/ug.html

Take a look at this article...it talks about the theory of undergravel filters, as well as the potential pitfalls that are a large part of the reasons many people have moved away from them.

COBettaCouple

i'm not sure i'd use the underground filters, especially in a bigger tank. I prefer other types of filters and avoid the UGFs.. i'd go with power filters or even a canister filter if you want to drop the money on one of those great filters.

sirdarksol

The biggest deal with undergravel filters (the article didn't seem to go into this at great length, but I only skimmed it so I might have missed it) is that the space under the filter can get clogged with detritus, especially in large tanks, such as yours. This can be mitigated by only using a smaller UGF, but it will, of course, not have as great of an effect. When the space gets clogged, there are pockets of water that don't cycle. The bacteria colonies quickly use up the oxygen in these areas and die off. So far, this has been covered in the above listed article. Once you have these pockets of stagnant water, a new type of bacteria begins to thrive. These bacteria are anaerobic (don't need oxygen). Most anaerobic bacteria create waste that is really toxic. For example, botulism toxin is produced by a type of anaerobic bacteria. These ones aren't any different, and begin producing waste that is a far cry worse than anything your fish or any of the types of bacteria that are normal to a tank can make. For awhile, this will remain ok, since the area under the filter is pretty much blocked off from the rest of the tank. But eventually, something will happen that will break a little bit of detritus out, such as a thorough vacuuming of the gravel, and the toxic water seeps into the rest of the aquarium.

Now this isn't always the case. This is just the worst case scenario. However, it's one that can kill your fish with little warning.
I've got an UGF that I'm planning on getting rid of as soon as I can get the fish out of the tank for a little bit.

Neville

Hey Sam, i have undergravel filters in all my tanks, have 3 undergravel filters in my 75 gallon angel tank.....not saying that sirdarksol is wrong but i don't see anything wrong with them, but that's only my opinion....u should buy whatever suits your tank; especially it depends on the fish u r going to keep...good luck.