ORP Concern

[demariners]

So I have an ozone unit and been stable 350-400mV readings for the last couple months. One of my fish got HLLE so I decided to remove carbon from the system and I noticed that the ORP significantly dropped to 180-225. The water does still seem pretty clear but I do notice a little difference. Any ideas? I also recalibrated the probe in case.

 

[Heliman]

It is very likely that between them, Ozone and GAC were removing most of the dissolved organics generated by your system...hence the stable ORP previously.

Once you remove the GAC, you removed one of the "filtration " elements, hence your water condition slowly deteriorates because Ozone cant do it on it's own now....hence the falling ORP.

The subject of GAC and HLLE is very hazy....IMHO the causality is when you allow particles of GAC to escape into the DT. I believe that if the GAC is properly contained in a reactor or a filter, then the HLLE risk goes away.

I have used ozone and GAC for 40 years....never had an instance of HLLE.

 

[demariners]

I had my GAC in a filter sock which was at the outlet of my skimmer. What are you suggestions? I have a vertex skimmer. and the outlet goes into a filter sock currently. I am inducing Ozone into it.

 

[Heliman]

OK, it seems that you had your GAC under control, the use of a filter sock would prevent any particles from entering your DT.

So I cannot offer any further suggestions in this respect, other than to repeat that it is not certain that GAC is specifically responsible for HLLE.

One other thing worth mentioning is the fact that your GAC was removing any (if any) free ozone from the system. In fact anybody using ozone should always run the effluent thru GAC, because free ozone in your DT will play havoc with bacteria, livestock etc.

Maybe your water is deteriorarting because you have small traces of free ozone...there is a salifert test kit available to check. Meanwhile, I personally would put your GAC back, or stop your ozone, it is too dangerous to run ozone without GAC.

My 2 cents worth.

 

[bertoni]

I think the current ORP level is fine, and I wouldn't worry about it. If you can tolerate the slight loss in water clarity, the tank should be okay.

Ozone can be dangerous, so I agree that caution is important. If you're worried, this article covers ozone equipment:

http://reefkeeping.com/issues/2006-04/rhf/index.php