Dlsb

[Nautilus29]

How come its ok in salt water to have a deep sand bed with anaerobic bacteria in it but not in freshwater? If you set up a sump with a large quantity of sand in it, wouldnt it help out with removing nitrates? Is there something Im missing here?

[cocoa_pleco]

you get gas pockets in FW, but in saltwater somehow everything works out

[Adrian]

I had read somewhere, that if you can get a deep enough gravel bed, you will get that bacteria, but the bed has to be pretty deep. It can not have any light at all penetrate it. No water flow either from what I understand.

I can't remember where I read it though.....

[MandyL]

How deep is too deep for FW?

[ILuvMyGoldBarb]

The problem in FW is that when you get pockets of anerobic bacteria you also get pockets of Hydrogen Sulfide gas. If that manages to get into the water column it can be potentiall harmful to your fish. That is why people who have deep sand beds in FW tanks should periodically rake their fingers through it to prevent the buildup of that gas.

Anerobic bacteria forms in areas where there is little to no oxygen. The bacteria in our filters and in normal substrates is arobic bacteria and it requires oxygen. This gets to the heart of why Wet/Dry filters are prefered in many FW tanks. The greater contact with the air allows for better formation of the bacteria. Because Anerobic bacteria forms in areas of no oxygen, it actually will use up the oxygen atoms that are in the nitrate molecules thus leaving just nitrogen which is gased off at the surface.