Carbon and ORP

[Thor2j]

So I recently started putting carbon in a reactor because my corals are starting to grow where some are now stinging each other. Nothing else in my chemistry has changed. Carbon has been there for 3 weeks and it is brs ROX. I used to run carbon but stopped about a year ago. When I stopped using carbon a year ago my ORP slowly fell 50 points. I thought nothing of it and all was well. Now my ORP has gone back up 50 points over last 3 weeks since I started carbon again. Anyone have an explanation?? Randy??

 

[Randy Holmes-Farley Verified Community Expert]

So I recently started putting carbon in a reactor because my corals are starting to grow where some are now stinging each other. Nothing else in my chemistry has changed. Carbon has been there for 3 weeks and it is brs ROX. I used to run carbon but stopped about a year ago. When I stopped using carbon a year ago my ORP slowly fell 50 points. I thought nothing of it and all was well. Now my ORP has gone back up 50 points over last 3 weeks since I started carbon again. Anyone have an explanation?? Randy??

It is not unexpected that reduced levels of organics will alter (raise) ORP. Highly oxidizing species produced in the tank (by light and other mechanisms) will tend to react with trace elements (e.g., converting ferrous iron, Fe++ to ferric iron, Fe+++) or with organics. The organics can then be a pathway to breaking down highly oxidizing species (e.g., in an extreme case, they are antioxidants like Vitamin C). Reducing organics reduces this way to breaking them down.

That may not be the only mechanism in play here, but I expect it is one of them.