Vitamin C and ORP

edosan · Apr 6, 2016

Hello Randy, I dose sodium ascorbate to my reef as a source of vitamin c
Is normal that ORP drops with adition of VC, but I was wonder, how much drop is normal, or what range is normal?

I have seen Drops from 400 to -50 and less, after dosing (I was so scared the first time), and no problems at all with anything on my reef, but is a huge drop, usually it drops from 400 to 100, and after a few ours is back in normal, even higher than before like 430.

ORP might be a way to measure how much VC my tank can absorve?... from 400 to 200 is normal?

Thanks in advance.

Randy Holmes-Farley · Apr 6, 2016

I cannot really say how much is "normal" because I haven't seen many detailed results from folks, and it will depend on the redox "buffering" capability of the water, which depends on things like the levels of various redox active metals (iron, etc.).

Monitoring the ORP might tell you when the vitamin C has all been destroyed (by reacting with oxidizers) or consumed, but I've not heard of anyone trying to do that.

edosan · Apr 16, 2016

Thanks Randy, even a small amount of vc make a big drop on orp. As you mention, only difference is how long does it take to come back to normal orp values.

Superlightman · Jul 15, 2021

has someone an explanation since? I experienced same a big drop from 30m ton1h than everythung is normal again even with a small quantity

Randy Holmes-Farley · Jul 15, 2021

Superlightman said:
has someone an explanation since? I experienced same a big drop from 30m ton1h than everythung is normal again even with a small quantity

Not sure what you mean by an explanation "since".

Vitamin C will always lower ORP. It is just a highly reducing compound (that is, by definition, what an antioxidant is).