Nitrate mystery

[Dan_P]

I guess I just don't agree with this assertion:

Adding surface area would not result in a higher growth rate and more bacteria stealing ammonia because food not surface area is limiting growth.

I'll say up front, we have no idea which organisms are actually taking up ammonia in an ordinary reef tank. Corals, bacteria, algae, and many species of each. Each will have somewhat different capabilities of taking up ammonia. That is, if we artificially lower ammonia more and more, some will drop out of the competition before others. So ammonia is not a hard and fast limitation at some fixed concentration that the tank stabilizes at, below which nothing changes. It's the mix of organisms taking it up that changes.

If any bacteria species are able to take ammonia at levels equal to or lower than corals, and if corals are actually getting any, then if we add more surface area, I think it is a perfectly viable hypothesis that more of the best ammonia scavengers will take hold and steal ammonia from corals. They could not do so to the same extent previously because space was limiting their ability to dominate the competition. But with space not a limitation, we can have more of the best scavengears that are able to beat out corals.

Ok, here is an experiment to test whether more surface area means faster ammonia removal by nitrifyers.

Establish a population of nitrifying bacteria, say Fritz Turbocharge, on a bed of aragonite (pre-saturated with phosphate). Observe ammonia draw down of a constant daily dose of ammonia (~0.5 ppm).

When draw down rates stable, transfer undisturbed aragonite bed to new aquarium to eliminate aquarium wall biofilms. Add identical but sterile aragonite bed

Monitor ammonia draw down after the same daily dose of ammonia. Initially rate could lower. Observe draw down for weeks. If increased surface area results in faster draw down rate, either from a population increase or from a more spread out biofilm, I would say that is evidence to support your hypothesis and a reason to explore heterotrophic bacteria response to more surface area.

If there is no surface area for bacteria, this does not necessarily mean there isn’t an effect, but the mechanism is more complicated.

How does this sound as preliminary experiment?

Edit: Maybe another study is to keep ramping up the ammonia dose to see when activity levels off. This would give us one reference point for how close an aquarium sand bed surface area is to being limiting. (I think that I might have seen this topic discussed in the aquaculture literature)