UV vs GAC post Ozone

[Randy Holmes-Farley Verified Community Expert]

I can be sure but well less than an hour

Maybe there was something somewhere in the setup that was low ORP (like stagnant seawater) that was released on startup?

 

[reef_ranch]

Maybe there was something somewhere in the setup that was low ORP (like stagnant seawater) that was released on startup?

No, the water circulates through the UV constantly. To confirm the effect, I turned on the ozone last night at 10:00 pm, set to run 10 minutes every hour. Here’s the ORP graph:

I turned off the ozone at 6:10. If the ORP rises I have to conclude that it is depressed by the O2 and UV combination. Or do I?? ‍

 

[reef_ranch]

Update to my situation. After trying various combinations, it appears that the reduction in ORP is cause solely by the UV and not any interaction between the UV and the ozone....

 

[Randy Holmes-Farley Verified Community Expert]

If the uv kills bacteria that later dump their low ORP internal contents, that could reduce ORP.

If the uv generates hydrogen peroxide internally, that too can lower ORP.

 

[reef_ranch]

If the uv kills bacteria that later dump their low ORP internal contents, that could reduce ORP.

If the uv generates hydrogen peroxide internally, that too can lower ORP.

I do have a minor bacterial bloom happening. Maybe I'll power through the low orp until the bloom is cleared up.
Does a properly functioning UV generate hydrogen peroxide?

 

[Randy Holmes-Farley Verified Community Expert]

I do have a minor bacterial bloom happening. Maybe I'll power through the low orp until the bloom is cleared up.
Does a properly functioning UV generate hydrogen peroxide?

I do not know how effective it is, but uv in seawater with organic matter can produce hydrogen peroxide.