[kwirky]

I think a fluidized bed filter, followed by a sulfate denitrator, then a calcium reactor of some sort is a perfect combination.

Liverock doesn't do much denitrating. Think of the people with reef tanks fighting with nitrates. in a FO setup, there isn't much denitrating going on.

the advantage of having your nitrification ON the liverock is so there's a CHANCE it'll be denitrated on the liverock. but i think it's pointless hoping for that, since you don't have the proper carbon fed to the anaerobic bacteria. do some research. there's like 50 different types of anearobic bacteria, and if they're not provided with the carbon nutrients, then you begin to harvest the bacteria that doesn't denitrifty the way we want. they end up producing more nitrite, and things like that.

one promising field, I think should be studied, and is being studied for waste water treatment in lower income countries, is cotton denitrification. using organic cotton as the filter bed, AND it is the carbon source. quite efficient, and low cost.

anyways, I'd rather have SOLID denitrification done in a reactor rather than HOPING it's done on the liverock. the macro algae will still grow on it, and the coraline.

the only drawback I see with fluidized bed filter is the oxygan intake. you NEED to aerate the water before puting it back in the tank. I've had fish die from using a fluidized bed filter on a heavily stocked tank because the return was fed below the water column.