Bleach-cured live rock causing ORP spike? Too high?

JollyReefer · May 23, 2018

Hi y'all,

I added a bleach-cured live rock to my reef tank two days ago. Since then, I've seen a massive ORP spike (from sub-300 mVs to nearly 450 mVs) via my Apex probe. I read a couple threads in which reefers discuss bleach dosing and subsequent ORP spikes with positive results. But in those cases, the ORP usually decreases shortly after the spike. My ORP has been trending upwards for two days. It looks to be peaking (hopefully) now.

I only bleach-cured one live rock, which I bought specifically to support a Ritteri anemone. I cycled my tank about a month ago with pre-cured live rock from an LFS.

Here's how I cured this one rock with bleach: I submerged the rock in a solution of 10% bleach/90% RODI water for one week. Then I rinsed the rock and let it dry outside for 3 days. Then I submerged the rock in fresh RODI water with a heater at 80 degrees for 1 week. Then I removed the rock, rinsed it, and put it in my tank.

Here's the ORP spike reading:

About my tank:
210g display, 70g sump.
I've had 4 clowns in the tank for 2 weeks. The clowns don't appear to be fazed by the ORP spike at all, but I'm a novice reefer, so take my opinion with a grain of salt.
The other Apex probe readings don't appear to have been affected much by the rock.

Couple of questions: Is my ORP too high? Should I do anything (including removing the bleach-cured rock) to address the now high ORP?

Please advise.

Thanks,
Jon

Bio-nut · May 23, 2018

Based on the information you provided I would say that your results are what you could expect. Typically oxidation with chlorine (in this case Sodium Hypochlorite) is accomplished at or around 100ppm solution at a pH of 6.5-7.0. I would say that depending on the demand that would have been sufficient for this application. For the application you describe above the concentration you used was around 5000 ppm and the pH was probably above any disinfection range (too high). I would pull the rock out and continue to flush it with RO/DI and monitor the pH of that solution before you put it back into you tank. you could pick up a bottle of free chlorine or total chlorine dip strips and monitor it that way until the level goes to 0 ppm.

One last thing ORP is not linear with oxidant levels. depending on the make up of your water you can have an ORP of 500mV and only have a 1.0ppm residual but in water with heavy organic load you can have an ORP of 250mV and a chlorine residual of 30ppm. ORP plateaus from about 1000mV yet at the level you can have a chlorine residual of 500ppm to 1300ppm.

If you are trying to disinfect with out the potential the side effects of Chlorine I recommend using Peroxyacetic Acid or (PAA) dilute solutions can be purchase for surface disinfection if you apply it directly to the rock it with disinfect very quickly. if you are trying to Bleach (whiten) the rock then continue with the chlorine but make sure that you rinse the rock and test the soaking water for chlorine and pH before you return to the tank.

Good luck and happy reefing!

JollyReefer · May 23, 2018

Bio-nut said:
Based on the information you provided I would say that your results are what you could expect. Typically oxidation with chlorine (in this case Sodium Hypochlorite) is accomplished at or around 100ppm solution at a pH of 6.5-7.0. I would say that depending on the demand that would have been sufficient for this application. For the application you describe above the concentration you used was around 5000 ppm and the pH was probably above any disinfection range (too high). I would pull the rock out and continue to flush it with RO/DI and monitor the pH of that solution before you put it back into you tank. you could pick up a bottle of free chlorine or total chlorine dip strips and monitor it that way until the level goes to 0 ppm.

One last thing ORP is not linear with oxidant levels. depending on the make up of your water you can have an ORP of 500mV and only have a 1.0ppm residual but in water with heavy organic load you can have an ORP of 250mV and a chlorine residual of 30ppm. ORP plateaus from about 1000mV yet at the level you can have a chlorine residual of 500ppm to 1300ppm.

If you are trying to disinfect with out the potential the side effects of Chlorine I recommend using Peroxyacetic Acid or (PAA) dilute solutions can be purchase for surface disinfection if you apply it directly to the rock it with disinfect very quickly. if you are trying to Bleach (whiten) the rock then continue with the chlorine but make sure that you rinse the rock and test the soaking water for chlorine and pH before you return to the tank.

Good luck and happy reefing!

Thanks for the very helpful information! Sounds like a well-founded approach.

Gareth elliott · May 23, 2018

I would keep an eye on your nutrient levels over the next few weeks make sure they dont go out of whack from anything released from the dead rock.

Bleach tends to gas off very quickly if your live stock was not effected yet i think you are in the clear after 2 days it being in the tank.

Randy Holmes-Farley · May 23, 2018

I personally wouldn’t do anything unless the ORP climbed into the upper 400s. A little Seachem Prime or vitamin C will bring it down if it keeps rising.

JollyReefer · May 24, 2018

Randy Holmes-Farley said:
I personally wouldn’t do anything unless the ORP climbed into the upper 400s. A little Seachem Prime or vitamin C will bring it down if it keeps rising.

Thanks a ton! I added a little Seachem Prime and the ORP levels decreased to sub-300 mVs again.

Randy Holmes-Farley · May 29, 2018

Has it stayed down?

JollyReefer · May 29, 2018

Thanks for following up, Randy. No, the ORP level rose again to over 450, so I added more Prime and took out the rock today. I'm probably going to do a 20% water change in the next day or so to try and keep the ORP level from creeping up again if it tries going back up.

Gareth elliott · May 29, 2018

By chance do you have ph reading? Has this also changed?

JollyReefer · May 31, 2018

Gareth elliott said:
By chance do you have ph reading? Has this also changed?

Yes, I have a ph probe, but the ph levels have remained the same (~8.0 - 8.05).

JollyReefer · Jun 1, 2018

@Randy Holmes-Farley, The rock has been removed from the tank for 3 days now. I did a 20% water change yesterday, which brought the ORP level down from 450+ to around 325. But that dip only lasted a short while. The ORP level rose again to 450+ a few hours later. It's been floating around that mark since then. At least it's stopped climbing, but I'm not sure how to bring the ORP level down more permanently. Seachem Prime only seemed to keep it down for a day or so. Someone suggested Chemi-Pure Elite. What do you think? Any further suggestions?

Randy Holmes-Farley · Jun 1, 2018

JollyReefer said:
@Randy Holmes-Farley, The rock has been removed from the tank for 3 days now. I did a 20% water change yesterday, which brought the ORP level down from 450+ to around 325. But that dip only lasted a short while. The ORP level rose again to 450+ a few hours later. It's been floating around that mark since then. At least it's stopped climbing, but I'm not sure how to bring the ORP level down more permanently. Seachem Prime only seemed to keep it down for a day or so. Someone suggested Chemi-Pure Elite. What do you think? Any further suggestions?

have you tried cleaning the probe? An upward ORP drift can be caused by algae growing on a probe.

There should be no need for anything if the rock that was an issue is out.