ORP/Ozone/pH/Alkalinity, etc.

[Itchy Trigger]

I recently started running ozone on my tank. I'm injecting it into an Avast ozone generator with a carbon post filter (an Avast MR5 reactor). All was looking good and ORP level rose from around 230 before ozone to around 310. Today I noticed that my pH had dipped from 8.2, where it normally sits, to around 7.75. I use a Milwaukee MC125 meter for ORP and pH, and I just replaced the pH probe, and it is calibrated accurately (double checked it to be sure).

My first thought was simply that injecting the ozone had caused the pH to drop, but then I decided to check some other chemistry. The tank is predominantly a FOWLR, though there are some corals in there (a few leathers and LPS). Anyhow, Calcium came in at 450. Magnesium at 1200, and Alkalinity was LOW - dKH around 5.5.

So clearly the low pH is more a result of the low alkalinity than the ozone injection. I do bi-weekly 50 gallon water changes (tank is 330g). I use Seachem Reef Salt and the SG is maintained at 1.025.

What would be the best way to get alkalinity up to acceptable levels? I was hoping to not have to dose two part. Suggestions?

 

[Itchy Trigger]

Would adding kalk to my ATO be the best method here?

 

[bertoni]

Some baking soda will be fine for raising the alkalinity. This calculator will help with a dose:

http://reef.diesyst.com/chemcalc/chem_calc3.html

Just dissolve the baking soda in a bit of RO/DI water to dose.

I'd watch the calcium level as well. The application of ozone might have changed the consumption rate of the tank.

 

[Itchy Trigger]

Thanks, Jonathan. I actually have been adding a baking soda solution (I used a calculator) over the past several hours, getting the alkalinity back up to a good level. I'm thinking about going forward though, and wondering if maybe adding something via dosing kalk would be a good idea. I wouldn't want this downward trend in the alkalinity to be an ongoing thing. Looking into something like the Avast kalk stirrer in line with my ATO.

 

[bertoni]

Ah, I see. Kalk is a fine way to add calcium and alkalinity. A stirrer should be okay, although I only used still reservoirs.

 

[Itchy Trigger]

Cool. Will continue reading. A follow up question... If I start dosing kalk might I be able to switch to a cheaper salt mix like IO? I'm currently using Seachem ReefSalt.

 

[bertoni]

Maybe. Kalk is a very dilute supplement, though.

 

[Itchy Trigger]

Ok well one step at a time I suppose. Let me start adding kalk and see if I can achieve some stability. Thanks again for the input!

 

[bertoni]

You're welcome! Good luck!

 

[Allentown]

What ATO are you using? If you are looking for something easy and use Tunze, get the tunze kalk bottle. No motors, no pumps, hooks right up to the Tunze ATO set up. Delivers saturated kalk with no issues of messing resovioir and or no issues with kalk running in the pump or accidential slurry being sucked up.

 

[Itchy Trigger]

I use the Avast ATO. Going to pick up an Avast kalk stirrer I believe. I do like the Tunze too - use that on my coral/invert qt.

 

[Itchy Trigger]

Following up on this... I started dosing kalk two weeks ago. My pH has come up to around 8.14. Alkalinity has gone way high (around 11.5 now), so I'm planning to cut back the amount of kalk I'm adding to the stirrer... The other thing I noticed was that my Magnesium levels had dipped to around 1200, so I supplemented with the BRS Magnesium mix, and got my Magnesium up to around 1350.

In another thread I mentioned that I also had a phosphate issue I needed to address. Phosphates were high - around 0.82 on my Hanna checker last time I checked, which was about a week ago). I started running GFO (regular granular for now) just last night. Checked my phosphates just now and they read 0.42. I double checked that reading - repeated the test and came back with 0.40. It doesn't seem possible that a reactor with fluidized GFO could reduce phosphate levels that fast, so I'm trying to figure out what could have caused this. The only thing I've done to the tank since my last phosphate reading of 0.82 was dose the Magnesium supplement. Could this have somehow impacted my phosphate reading?

Edit: Interesting... Just read about how dosing kalk can potentially reduce phosphates... So perhaps that is what is happening. Lower phosphates is what I'm after, so whether it's by GFO or kalk, I'll be happy. I want to understand what's happening though, of course.

 

[bertoni]

The magnesium supplement will not affect the phosphate reading in any measurable way, if at all. Dosing Kalk might affect the phosphate level directly, although that's not been shown to happen. Kalk definitely can affect the phosphate level indirectly by encouraging growth, though.

 

[Itchy Trigger]

Ok. Must be largely due to the GFO reactor then. Phosphates tested at 0.13 this morning.

 

[bertoni]

GFO can reduce the phosphate level in a tank very rapidly. Your numbers are well within normal expectations.

 

[Itchy Trigger]

Cool, good to know it can and does work that well!

 

[tmz]

How is the ORP now? Are you still dosing ozone? Part of the initial ORP rise you noted from 230 to 310 was related to the drop in pH even though it wouldn't cause the drop. They have an inverse relationship.

 

[Itchy Trigger]

ORP is currently reading 346. pH is 8.02.

 

[tmz]

That sounds good to me.

 

[Itchy Trigger]

Hmmm. My ORP continues to rise. The generator is plugged into my Milwaukee MC125 controller and set to come on if ORP falls below ~325 or so. The generator is off but ORP is now at 384. Was 369 yesterday and I haven't seen the generator on. How would ORP continue to rise without further ozone injection? And should I be concerned it will go too high?