Undergravel Filters

[Kyra]

The ones with the airstone, tube and giant tray that you dump the aquarium pebbles on. My pet store clerk told me it was more of a biological filter as opposed to an automatic one like most waterpump filters, and said that it's okay to run both, but I wasn't completely sure on whether purchasing one for my tank or not would be worth it. You use the airstone to aeriate the water, but how does this affect filtering? Will my 20 gallon tank be fine without it? Do these help remove ammonia or fish waste easier?

 

[KcMopar]

Running both is fine, I have not used an under-gravel filter in about 2 decades. They have many filters now that have places for beneficial bacteria to grow besides the substrate. A filter with the bio wheel or the plastic trays for bacteria growth work great. The air stone deal is not needed if you have good water surface movement, surface movement is how your water gets oxygenated the bubbles in the water do nothing, its the agitation at the surface that does the work. Just me sure not to clean the bio wheel or growth trays.

 

[skjl47]

Hello; I have used the UG filters alone and in combination with other types. I tend to do the combo setup anymore because a hang on back (HOB) filter, or other external type, will physically remove some of the detritus. With a HOB filter I like to have an air bubbler if using one alone. Another setup that has worked for me is a HOB and a bubble operated sponge filter, with the spong filter buried in the gravel.
One good thing about an UG filter is that they rarely, if ever, fail. The air pumps do fail from time to time. I have gone thru many external filters problems without any UG filter issues (not counting the air supply problems).