Low pH

Smugmushroom · Sep 30, 2017

Hi Doc,

I'm stuck between a rock and a very hard place right now.

My pH is acting really strange.

Tank details:
110g with 25g sump, overall 4 years old (upgraded in May this year, keeping everything).
Running Bubble Magus Curve 5, BM 100 reactor with GAC (1kg fresh this morning), Caulerpa Prolifica in my fuge.
Mixed reef tank, mostly soft coral aswell as Monti, Frogspawn & Duncans.
Livestock is; Regal tang 4", Naso tang 4", Convict tang 3", Sailfin tang 4", Yellow tang 4", 2 false percula clowns ~2.5", Pearlscale butterfly 2", Bicolour angel 2", 2 green chromis 2", Engineer goby 13".
Skunk cleaner shrimp, Nassarius snails, Cerith snails & Astraea snails, Red leg hermit crabs, Maldive starfish.

Test results:
NH3 = 0.0
NO2 = 0.0
NO3 = 2.5
PO4 = 0.06
ALK = 12.1 dKH
Ca = 480
Mg = 1470
pH = 7.7

skimmer has outside air supply, windows open in tank room incase of CO2 saturation, zero change.

I don't understand why my pH is so low, according to Randy's chart, at that ALK even with elevated CO2 I should be reaching 8.0.

My next thought was high organics/decomposition, but all live stock is accounted for, all corals are "out", feedings are conservative. Fresh carbon, wet skimming, fuge and test results don't indicate to me a high unresolved organic load.

I have ordered a soda lime CO2 scrubber to try. I have double checked by results with 2 different brands of tests, my pH probe and pH dip meter are matched to within 0.05 and liquid pH test confirms.

I'm out of ideas?

TIA

Randy Holmes-Farley · Sep 30, 2017

If indoor CO2 is very high and needs to stay high for some reason, there may not always be perfect solutions.

Have you recently recalibrated the pH devices?

Have you done both aeration tests in my low pH articles?

pH And The Reef Aquarium
http://www.reefedition.com/ph-and-the-reef-aquarium/

The Aeration Test

Some of the possible causes of low pH listed above require an effort to diagnose. Problems 3 and 4 are quite common, and here is a way to distinguish them. Remove a cup of tank water and measure its pH. Then aerate it for an hour with an airstone using outside air. Its pH should rise if it is unusually low for the measured alkalinity (Figure 2). Then repeat the same experiment on a new cup of water using inside air. If its pH also rises, then the aquarium’s pH will rise simply with more aeration because it is only the aquarium that contains excess carbon dioxide. If the pH does not rise in the cup (or rises very little) when aerating with indoor air, then that air likely contains excess CO2, and more aeration with that same air will not solve the low pH problem (although aeration with fresher air should). Be careful implementing this test if the outside aeration test results in a large temperature change (more than 5°C or 10°F), because such changes alone impact pH measurements.

Smugmushroom · Sep 30, 2017

Thanks for such a quick reply Randy. Both probe and meter were calibrated approx. 6 weeks ago using 2 diff. solutions a 6.86 and a 9.18. I have just setup the outside air test and will update within the hour. Thank you.

Randy Holmes-Farley · Sep 30, 2017

Smugmushroom said:
Thanks for such a quick reply Randy. Both probe and meter were calibrated approx. 6 weeks ago using 2 diff. solutions a 6.86 and a 9.18. I have just setup the outside air test and will update within the hour. Thank you.

Just to clarify, I know that some meters can certainly accept buffers at any pH value (mine can), but some cannot, and expect an exact value like 7. Did the meters read the buffers correctly after calibration

Smugmushroom · Sep 30, 2017

I used the sachets of buffers that came with the probe and meter on purchase, both had the same pH ranges and were mixed accordingly and gently heated to 25C as instructed.

Smugmushroom · Sep 30, 2017

Results : Approx 1L of tank water, aerating with a wooden air diffuser and outside air. Nearly a 1C drop in temperature of the sample at final test. Digital dip meter was 7.66 before the test, 8.07 @ 25 minutes. Approx. 1L fresh SW test with indoor air, windows closed, 8.26 at start and now 8.06 at about 10 minutes into the test.

Smugmushroom · Sep 30, 2017

I have 2 wave makers providing surface agitation of the display tank, and a powerhead in sump doing the same. Skimmer has an outside feed also, how much more aeration can I practically achieve? From the results there is definitely a CO2 problem.

Smugmushroom · Sep 30, 2017

Result of fresh SW sample using indoor air @ 25 minutes, pH is reading 7.83 from a 8.26 start. I'm not sure of the average modern home CO2 concentration, but that seems to me quite a lot of CO2. My family is 4, 2 adults and 2 children. Natural gas central heating, the boiler is downstairs in the garage.

Randy Holmes-Farley · Sep 30, 2017

Smugmushroom said:
Result of fresh SW sample using indoor air @ 25 minutes, pH is reading 7.83 from a 8.26 start. I'm not sure of the average modern home CO2 concentration, but that seems to me quite a lot of CO2. My family is 4, 2 adults and 2 children. Natural gas central heating, the boiler is downstairs in the garage.

Its high, but not unusual.

Smugmushroom · Sep 30, 2017

So from these results, I think the soda lime will definitely help somewhat. I'm already at the top end of what I can do chemically with the water. Is there anything else I could do? Bearing in mind that winter is approaching and I am in the UK. BTW thanks very much for your help, the simple tests have revealed the culprit.

Randy Holmes-Farley · Sep 30, 2017

When low pH is driven by elevated home air CO2, the following things can help raise the pH:

1. More fresh air into the house.
2. Less tank top aeration
3. Outside or scrubber air to skimmer inlet
4. Use of limewater (kalkwasser) for calcium and alkalinity
5. As much photosynthesis as possible, even adding nutrients if needed, including main tank and refugia

Smugmushroom · Sep 30, 2017

Thanks Randy, I was initially surprised by No.2 but it makes sense of course to reduce the equilibrium of home air, whilst providing clean air in my skimmer. I have just lowered my wave makers to calm the surface of the main tank. My scrubber should arrive on Monday. I have also just ordered a doubling of my macro algae for the fuge. I already drip CA(OH)2 so I'm pretty much out of options now, fingers crossed the scrubber does its job

Thank you again, and have a good weekend!

rob safron · Sep 30, 2017

I feel your pain. pH is very frustrating, I know. For months now I get up to 8.1 during the day and drops to a low of 7.73. Very big swing. I have my skimmer hooked to CO2 scrubber and that is piped to outside. We have had great weather in St. Louis and all our windows have been open this week. I even have a winder right next to the tank that’s open. I didn’t get any budge per my 2 Apex pH probes after 7 days of open windows. Wish there was an easy answer but never is.

Smugmushroom · Sep 30, 2017

I'm just glad I know the cause, now I can work on a solution

Smugmushroom · Oct 3, 2017

update - got up yesterday morning to the biggest bacterial bloom I have ever seen. And i'm not stranger to carbon dosing, however no carbon dosing had been done and I haven't run pearls for nearly 8 weeks (going back to basics) I couldn't see into the tank more than half an inch. my pH probe was reading 7.29, I had a mini heart attack! I had a twin airpump still running in the sump from the tests I did in this thread, but all I can think is, my tank has been nuked!
First step, open all the windows, let as much fresh air in as possible, remove the glass covers of the tank. Place 2 air pump hanging out of the window for the sump, skimmers bubbling but not pulling, add an airstone to that to turbo charge it. Blue lights are on, I can't see any signs of life inside. I drain 100L out of my 500L system, I know a water change won't change a bacterial bloom but i'm trying to stabilize the tank, 100L of fresh SW goes in. And I wait an hour for it to properly mix, then the full barrage of tests begin. Ammonia 0.1, Nitrite 0, Nitrate 0, Phos 0, Ca 460, KH 11.5, Mg 1400, pH has now risen to 7.4. skimmer is pulling some nasty stuff out but very slowly. fast forward 7 hours, I spot my yellow tang at the front of the glass, not clearly but its definitely him, ALIVE!! another 100L water change and I can just about see the rocks, and my other fish appear 1 by 1

a quick prayer of thanks to any deity that's listening, and I hunker down for a long night. This morning, still couldn't see much, pH had risen 7.53, bloom must be reducing. 12 hours at work later and I can see my whole tank, still a touch cloudy but I can see well enough to establish a damage report... only the Duncan is ticked and not showing much PE. pH now 7.64 with a co2 scrubber inline to the skimmer.
The only thing that changed to cause this was me bubbling air into the sump to try to drive out excess CO2, so I must have had a massive hidden organic issue that properly reared its head when more oxygen was added to the water? I'm grasping at straws really but holy **** that has to be my worst experience of reefing so far.