Posted by j0nn13 on March 09, 2003 at 06:51:22:
In Reply to: Function of Undergravel Filter posted by lacie143 on March 09, 2003 at 00:02:23:
It sucks water down through the gravel and then up an uplift tube back into circulation. De-nitrifying bacteria grow on the gravel and as the water is sucked through the gravel and therefore the bacteria, ammonia and nitrite are changed to nitrate.
I Think :-)