Bacterial blooms when stopping carbon dosing?

[Sebae]

Hello all,

I have a coral quarantine system both to check for coral pests and to prevent cryptocaryon or other fish parasite transfer. Thus, there are no fish in the system. Despite having a low need to input nutrients into the system without fish, I was somewhat naively carbon dosing. I had undetectable NO3 and PO4 but I then began having faded SPS. I sought to raise my nutrients and did so over the course of a few days (NO3 ~5 ppm, PO4 0.05 ppm). I haven't dosed any carbon source in several weeks.

I now have a persistent cloudiness to the tank. I tried running my UV sterilizer which has worked for these blooms in the past but haven't had much progress this time around.

Basically, what would cause a bacterial bloom (I'm assuming that is what this is) when one quits carbon dosing cold turkey?

Thanks

 

[clsanchez77]

Is it possible you had a supply of carbon in the water column awaiting available nitrates and phosphates? Usually carbon is the limiting factor...but since you were dosing it with little demand, perhaps you unknowingly stocked up on it. If that is the case, the problem should resolve itself with time, I would definitely keep running the UV and make sure you have a good water turbulence at the surface. Dose the nitrate and phosphate slowly because if my speculation is correct, once that carbon is fully used up, you could have a spike in nitrate and phosphate.

 

[Sebae]

That certainly makes sense but if there were an untapped supply of carbon that was just waiting on a rise in N and P to take off... Shouldn't I be able to pretty quickly drop that down with a large water change?

 

[clsanchez77]

That certainly makes sense but if there were an untapped supply of carbon that was just waiting on a rise in N and P to take off... Shouldn't I be able to pretty quickly drop that down with a large water change?

Yes, but it will only come down proportional to the water change. So if you do a 25% water change, you will only reduce/correct the carbon (and everything else) by 25%.

 

[Randy Holmes-Farley Verified Community Expert]

I suspect it is a rush of available nutrients and lack of carbon source to feed the bacteria that were consuming it (likely growing on

That certainly makes sense but if there were an untapped supply of carbon that was just waiting on a rise in N and P to take off... Shouldn't I be able to pretty quickly drop that down with a large water change?

Phosphate is not readily removed by water change since it can bind to rock and sand. Hence a 100% change does not remove all of it. For nitrate, water changes can remove it, but the bacteria are also removing it and I wouldn't do anything special. A bloom is rarely any concern, aside from O2 consumption..

 

[Randy Holmes-Farley Verified Community Expert]

Is it possible you had a supply of carbon in the water column awaiting available nitrates and phosphates? Usually carbon is the limiting factor...but since you were dosing it with little demand, perhaps you unknowingly stocked up on it. If that is the case, the problem should resolve itself with time, I would definitely keep running the UV and make sure you have a good water turbulence at the surface. Dose the nitrate and phosphate slowly because if my speculation is correct, once that carbon is fully used up, you could have a spike in nitrate and phosphate.

That's a possibility.