Quote:
Originally Posted by karimwassef
OK - QUESTION TO THE CHEMISTRY GUYS!
Randy, Jonathan -
THEN! IN THE SAND OR OTHER ANAEROBIC MEDIA, DENITRIFYING BACTERIA CONVERT THIS INTO NITROGEN GAS (correct?).
Why the caps? because I think the N2 is the problem. We've associated sand beds with dinos and cyano... but I think it's the fact that a functioning sand bed will generate nitrogen gas.
The Nitrogen gas, along with any waste, becomes a food source... for nitrogen fixing creatures... DINOS, CYANO, PHYTO.
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Karim, your description of the N cycle in tanks is correct but I think you are being confused by papers talking about "N" when they mean nitrate/ammonia or nitrite. Nitrogen gas is already present in the aquarium at very high concentrations, because it is 80% of our air. Increasing flow would probably increase the net amount of N2 gas. Dinos and plants can't do anything with N2, nitrogen gas. Dinos can use (almost) every form of nitrogen *except* N gas. They probably prefer inorganic (ammonia, etc) forms of nitrogen because they don't require processing to be useful.
Cyano CAN fix its own usable nitrogen from N2 gas. (This may be its claim to fame in the ocean) It probably likes the sandbed because there's more available phosphate in the low-flow spots where detritus accumulates. We see cyano before dinos because environments with very low available nitrate/nitrite/ammonia are hostile to green plants, and cyano is making its own N. It also stores phosphate. The dinos associate (or eat, or even farm) the cyano and other bacteria, taking advantage of the P and N. Dinos can therefore take advantage of the organically-bound nitrogen in the bacteria cells, plus they can suck up inorganic nitrate/etc from the water. Dinos switch strategies according to local conditions, so if the aquarist is actively reducing available inorganic (ammonia, nitrate) nitrogen, they will predate on bacteria more.
So you're right that bacteria may be part of the problem, but really there is no practical way to sterilize a reef tank without killing *everything*. UV doesn't affect surface-living bacteria, and I saw an AA article saying it doesn't actually affect the pelagic populations much because bacteria can reproduce so quickly.
hth and the chem gurus will correct me if I'm wrong,
Ivy
PS interesting note in that paper! Ostreopsis stops/reduces its toxin production under low nitrogen conditions. So taking up all the available nitrogen by competition (dirty) or direct removal (clean) may make dinos less problematic. Also, diatoms can have symbiosis with cyano. Didn't know that either, cool.