Help with low pH but good Alkalinity

[whybenormal]

75 gallon tank with Triton 34 sump.
I've never gotten the pH over 8.1, but the rest of the parameters have been good.
The last few months though it has trended lower.
This morning when I got up it was 7.1, which was its low last night. The high for all day yesterday was 7.89.
The night before it reached a new low of 7.68.
I'm not dosing anything, as I don't yet really know what to dose. I do have some corals, mostly soft, and a few LPS.
A couple of my clove polyps have now died.

I have API & Monitor tests, but added a Seneye, just for a 2nd opinion. Then added another pH monitor that hangs in the tank that I can independently calibrate to double check the Seneye - just bc I couldn't believe my pH was so low.
Then I added a big airstone in the skimmer compartment of the sump. It helped a bit.
line running outside - made no difference, but we have doors open a lot anyway
Better regugium light for the chaeto (Tunze Ecochic)
C02 scrubber

Tests as of Tuesday (weekly test day) 11:30 am
Temp - 77.4 (pretty normal)
Salinity - 1.022 (working back to 1.025)
pH - 7.7 ** See above**
Alkalinity 9.52
Nitrites - 0
Nitrates 20
Phosphate .25
Ammonia .25
Calcium 400
Magnesium 1100

Any help is greatly appreciated!

 

[Duffer]

i'm a firm believer don't chase PH numbers, if things are fine leave it alone, but on your parameters i do have some opinions as follows: what i did find is adding a line to the skimmer that leads to outside.

Nitrates a bit high
Phosphates are high, want around .05
clacium i like them around 450, 400 not bad
Mag is low, get them up to around 1350, mine are around 1400 and i find my LPS like a higher mag.

 

[whybenormal]

I definitely don't chase, as I said, I'm dosing nothing, but my cloves are now dying. And the pH is bottoming out as low as 7.68.
That is with the skimmer, CO2 scrubber and line outside.

As far as starting to dose the Magnesium, I'm not sure how to do it, as in how much at a time. I have the Quantum products.

 

[Duffer]

what salt do you use?

a re you doing weekly water changes?

most times with your tank size water changes can get your main parameters to a nice level..

 

[whybenormal]

what salt do you use?

I've been using Reef Crystals, though just used up the bucket

 

[Duffer]

you can manually dose mag..reef cystals tends to have a low mag

 

[whybenormal]

I've been doing more of a monthly water change. And now have to get more salt before I can do anything. I wanted to switch to something better. I'd hoped to switch to Quantum LPS, but can't get my hands on it.

 

[Randy Holmes-Farley]

IMO, if pH 7.7 is accurate, I'd raise it. It is stressful to calcifying organisms.

There are many ways, including more fresh air to the room or to a skimmer inlet, CO2 scrubber, reverse lit refugium, etc.

 

[Randy Holmes-Farley]

you can manually dose mag..reef cystals tends to have a low mag

Reef Crystals does not have low magnesium, IMO.

The reason magnesium is low here (if accurate) is because the salinity is much too low.

If he raises his salinity to 35 ppt (sg = 1.0264), the magnesium will rise from 1100 to 1320 ppm.

 

[whybenormal]

IMO, if pH 7.7 is accurate, I'd raise it. It is stressful to calcifying organisms.

There are many ways, including more fresh air to the room or to a skimmer inlet, CO2 scrubber, reverse lit refugium, etc.

What else can I do when I'm doing all of those?
And to the best of my ability, I've checked the accuracy of the pH with 2 different water based tests and the Seneye, another monitor that I calibrated, and yet another pH meter my husband just ordered.

 

[whybenormal]

Reef Crystals does not have low magnesium, IMO.

The reason magnesium is low here (if accurate) is because the salinity is much too low.

If he raises his salinity to 35 ppt (sg = 1.0264), the magnesium will rise from 1100 to 1320 ppm.

I'm working to slowly raise the salinity back up to 1.025. It is actually 1.023 today.

 

[chipmunkofdoom2]

Something feels off. With your alkalinity being relatively high, an outside air line, CO2 scrubber and having doors and windows open frequently, I would think your pH should be higher.

As a sanity check, try taking a cup of tank water outside, aerating with an air stone for 10 - 15 minutes, then measure the pH. After aerating, the water in the cup should be between 8.1 and 8.3. If it's not, something's wrong with your pH measurement devices.

 

[Randy Holmes-Farley]

What else can I do when I'm doing all of those?
And to the best of my ability, I've checked the accuracy of the pH with 2 different water based tests and the Seneye, another monitor that I calibrated, and yet another pH meter my husband just ordered.

If you are doing all of those well, the pH should not be low.

Try this aeration test:

pH and the Reef Aquarium - REEFEDITION

by Randy Holmes-Farley For many aquarists, pH is not something that they have much experience with aside from their aquarium. For many, pH is almost a black box measurement: something to be considered, but whose physical meaning makes little sense to them. This article will Read more here...

www.reefedition.com

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.

 

[whybenormal]

Something feels off. With your alkalinity being relatively high, an outside air line, CO2 scrubber and having doors and windows open frequently, I would think your pH should be higher.

As a sanity check, try taking a cup of tank water outside, aerating with an air stone for 10 - 15 minutes, then measure the pH. After aerating, the water in the cup should be between 8.1 and 8.3. If it's not, something's wrong with your pH measurement devices.

I'm trying this now

 

[chipmunkofdoom2]

I'm trying this now

Per Randy's post above, looks like you should aerate for about an hour, not 10-15 minutes as I had originally said. Sorry about that!

 

[whybenormal]

Per Randy's post above, looks like you should aerate for about an hour, not 10-15 minutes as I had originally said. Sorry about that!

Even for just the 10 minutes I saw an increase in the cup of water from 7.8 to 8.0. Enough to know that, in spite of everything we have been doing, we just need to do more of it!
So I'm off to buy more airline tubing and figure out how to get more aeration going.

 

[whybenormal]

This is just a little update. We got an airpump with a line running outside running into the skimmer chamber, and another airstone running into the tank just for good measure. We got all the way up to 7.9 (from my low of 7.71) before it started falling for the evening. Now, with all the extra aeration since 7pm (it is now 10:15) I'm down to 7.69 (!) Worse than last night!

 

[Randy Holmes-Farley]

This is just a little update. We got an airpump with a line running outside running into the skimmer chamber, and another airstone running into the tank just for good measure. We got all the way up to 7.9 (from my low of 7.71) before it started falling for the evening. Now, with all the extra aeration since 7pm (it is now 10:15) I'm down to 7.69 (!) Worse than last night!

Your aeration experiment in the cup was done using inside or outside air?

The "another airstone" above was using inside or outside air?

 

[14 foot reef]

I'm working to slowly raise the salinity back up to 1.025. It is actually 1.023 today.

Check co2 in your home. if its high, you'll almost never get your PH up. Kalk dosing reverse lighting schedule will help.

 

[whybenormal]

Your aeration experiment in the cup was done using inside or outside air?

The "another airstone" above was using inside or outside air?

Both using outside air. The air pump I have has two separate air pumps inside, so I ran both lines in to the tank. My husband ran 1/2" tubing from outside to the pump inlet.