Low pH and ORP

DiZASTiX · Apr 19, 2018

Why are pH and ORP low? I expect pH to be 8.0 to 8.3 and ORP to be certainly at least 100 points higher. In the past, without much of a biological load, ORP rose quickly (and, using a controller), topped off at 450. pH and ORP seem to be both rising over the course of several days, when zoomed out at that level.

Given that pH is the key parameter of question, I've measured it chemically using a test kit and using a probe. Both confirm my test results.

I have 40 gallons of sea water with the following measured parameters. Tests were repeated on a regular basis and found not to deviate outside de minis amounts:

pH: 7.87
Salinity: 1.026 SGORP: 247 and rising slowly though falling too.
Ammonia: 0 ppm
Nitrite: 0 ppm
Nitrate: 0 ppm
Phosphate: 0 ppm
Calcium: > 550 ppm
Magnesium: 1500 ppm
Alkalinity: 13.8 dKH
Copper: 0 ppm
Temperature: 27 C

Established time: ~1 month

Water is highly turbulent using Tunze Turbelle. The display tank has so much flow that I had to turn down the Turbelle, as no matter how much I positioned it, combined with the Reef Octopus VarioS-6 return, water would blast out the front or sides.

Water is on enclosed space and windows are seldom open.

This sounds totally random but it's not. It's my coral reef aquarium, and I think, but can't confirm that corals and other animals are dying because of it. Whatever you have is great!!

So far I've dosed kalkwasser / limewater, which has a pH of 12, and that only briefly raises pH before it settles.

I'm going to be trying opening windows (hypothesis: too much CO2 lowers pH), but the flat is pressurised and air is blown out the window due to shared hallway ventilation.

mahindra.dev · Apr 19, 2018

@Randy Holmes-Farley can give more details and he has multiple articles.

That said dont chase ORP as you are not using O3. I clean my probes time and again. If algae build up near the ORP probe, your values will always be higher.
And yes pH is lower because of Co2. Now you do see beautiful reeefs with 7.8-8.1 swings day to day. I stabilized my pH swings to 0.1 by adding a refugium and running is 16hrs a day. I didnt go the scrubber route.

Your alk is def higher. In trying to chase pH dont mess with Alk. 8-10 is recommended

DiZASTiX · Apr 19, 2018

To clarify, I am using O3. I haven't touched kalk: I tried dosing kalkwasser, but the alkalinity was in the 13 range or higher prior to that. I've since stopped dosing kalk, and have dosing pumps put out 50 mL a day each of AquaForest Component 1+, 2+, and 3+, as part of the Balling Method. Based on the next set of tests, I'll be adjusting the dosing pumps (likely reducing the dosages).

I'll go and clean the probes of algae and report back.

Thank you for your input.

Brew12 · Apr 19, 2018

DiZASTiX said:
To clarify, I am using O3. I haven't touched kalk: I tried dosing kalkwasser, but the alkalinity was in the 13 range or higher prior to that. I've since stopped dosing kalk, and have dosing pumps put out 50 mL a day each of AquaForest Component 1+, 2+, and 3+, as part of the Balling Method. Based on the next set of tests, I'll be adjusting the dosing pumps (likely reducing the dosages).

I'll go and clean the probes of algae and report back.

Thank you for your input.

Have you tried spreading out your kalkwasser dosing to between 50 and 100 small doses per day? The chemical reaction by which kalk consumed CO2 (and raises pH) is fairly short lived, but can be sustained through many small doses.

If I recall correctly, 45mL of saturated kalkwasser is the same as 1mL of Randy's 2-part recipe. I'm not sure how the AquaForest stuff compares. Depending on your evaporation, you could do 75 doses of kalk at 5mL per dose and only reduce your AquaForest dosing by under 10mL per day.

Randy Holmes-Farley · Apr 19, 2018

I don’t see any reason to be concerned about the ORP. It might be wrong, it might be from the trace elements added, or other reason.

Did you recently calibrate it?