View Full Version : How do you determine if the tank is Nitrogen or Carbon limited

03/26/2012, 11:10 AM
No one answered my question, so I put the same question here.

I often hear Nitrogen or Carbon limited in RC, but how do you determine if the tank is Nitrogen or Carbon limited. I know the Carbon and Nitrogen should be balanced, but not sure the ratio.

Also, if the tank is Nitrogen or Carbon limited , what would be happened in your tank? My feeling is that Nitrogen limited causes to decrease the Phosphate reduction rate. And Carbon limited causes to decrease the Nitrate reduction rate.

Randy Holmes-Farley
03/26/2012, 12:27 PM
Well, a tank isn't necessarily limited in either, depending on what is going on. Also, you'd need to be specific in what process you were asking about being limited.

If you mean limited in heterotrophic bacterial growth, you need a source of N, P and organic carbon for that process. If one is limiting, then the other two will not decline as fast as they might otherwise do so. Two or more of these can also be limiting at the same time.

The only way to tell what is limited in any given scenario is through addition of one and see if the other two change. :)

In general, if you have measurable nitrate and phosphate, and are not dosing organic carbon, the organic carbon is almost certainly limiting. :)

03/29/2012, 02:03 PM
Thank you for your reply and sorry for my late reply.

I recently bought two products. One is NeoNitro from Brightwell and another one is NO3PO4-X. Both products specify the dosage based on Nitrate and PO4 concentration.

If PO4 does not decrease without dosing Carbon source, does it mean Nitrogen limited?

Randy Holmes-Farley
03/30/2012, 06:50 AM
I am not sure what is in those products, but the second one is a carbon source. :)