Originally Posted by eighty80
almost done reading your articles there very informitive and to the point. easy to read. i came across were you state that biological filters could be bad for plants. i have a undergravel filter with 2 power heads this is considerd a biological filter right? if so will i need to turn off the power heads in order to have live plants.
If the tank has been running with fish in it, you can't just turn off the undergravel filter. It will pollute the tank and possibly kill the fish.
Like any filter, an UG works by drawing water through the media; in this case, the media is the gravel substrate above the filterplate. Aerobic bacteria colonize and build up in the substrate (media), including most of the nitrifying bacteria that convert ammonia and nitrite, and these require oxygen which they obtain from the water passing through; if the flow of water is stopped, the bacteria will be starved of oxygen and die, and it only takes a few hours. This is my chief objection to UG filters; if the power goes out for several hours, the bacteria will die. Not only does this cause problems with nitrogen gas and such, but it kills most of the nitrifying bacteria which causes a new cycle in the tank--if the fish live so long.
It is possible to have a planted tank with an UG filter, but it is an obstacle. Not only due to the above concern on its own, but the plant roots will clog the filter plate impeding the flow of water, and this again leads to the above issue. Removing the UG filter means taking out the gravel and rinsing it to free it of most of the bacteria. Better to start with a clean system. If you go this route, establish your new filter first, by which I mean, set it up in the tank and run it for a couple weeks (without rinsing or cleaning it) to establish a bacteria colony. Then it will help when the UG is removed and the gravel rinsed.
For a 45g tank you could use a canister filter or a good sponge filter. The powerheads if left would create additional issues by the excess water flow, depending upon how powerful they are of course.