Low PH ikn FOWLR

[paulsvang]

Any suggestion?

My PH has been really low. It seems to be a bit better now but I'd like it to be in the 8s.
I've tried using a vacuum tube to my skimmer with the other end outside to ensure I'm getting good air but after a day of it, the ph is still the same. It swings between 7.6-7.9. Mostly around 7.8.

Any ideas would be appreciated. I have kalkwasser but I was told it may increase my alk.

Calcium 520
dkh 9
nitrate 0
posphate .25
ph 7.8 - as low as 7.5 about 2 weeks ago
Salinity 1.024
Temp 77 *F

Red Sea Reefer 350 with 70lbs live rocks.
Tank is about 2 months old right now.

Sump is full of red gracilaria, ulva and caulerpa brachypus.... and they are growing very well.

 

[bertoni]

7.8 is a fairly common pH level for a tank in a house with the windows shut. That entire range should be fine for fish. One easy thing to try is to make sure that the water surface is free of any film, and is getting a good rippling action. That helps in only a very few cases, but it's easy to check. You could consider lighting the sump during the night, which is likely when the pH is the lowest.

Kalk might raise the alkalinity over time if the tank has very little coralline or other calcifying organisms.

An air exchanger or scrubber might help. The scrubber might help if used only for the skimmer, but that seems unlikely given that the air tube leading outside didn't help. I'm not sure how practical scrubbing the air over the tank might be. Is the system enclosed in any way?

 

[paulsvang]

the water surface is clear. I have a maxspect gyre running pointed up towards the top. the system is not enclosed. the top is open. The sump has no cover. The water is fine when freshly mixed. Its at 8.2 however when it's in the tank, it drops down to 7.8. I was wondering if there's anything I can do to increase the pH. I hope to get some corals in the tank next month. Just hoping to get the pH where it should be.

 

[dkeller_nc]

Depending on how often you change water and what percentage, how stocked your tank is, and whether or not you run GAC, it may be that you've built up enough dissolved organics that it's depressing your pH. As Jonathan notes, a high DOC (at least within reason) is no detriment to the fish, and isn't generally much of a problem for most corals.

One other comment - you don't mention how you're measuring pH. To do this accurately, you need a pH meter with a properly calibrated probe. pH test kits are notoriously inaccurate, and might lead you to do something drastic that isn't going to be good for your fish.

 

[paulsvang]

pH is measured using a probe. Probe is accurate as the freshly mixed saltwater is at 8.2. 10% Water changes once a month. I have a small naso, medium yellow tang, baby clown fish medium blue tang, 2 cleaner shrimp and a cleaner wrasse. Theres no GAC on this sytem.

 

[tmz]

PH under 7.7 is a concern for calcifying organisms like some corals. Skeletal mass composed of calcium carbonate may begin to dissolve at that level or lower.

Kalk is calcium hydroxide. It adds calcium ; the hydroxide binds CO2 forming carbonate alkalinity. The reduced CO2 raises the pH ; the carbonate increases the alk.

When you tried the outside airline to the skimmer venture ,was the tube diameter large enough? Sometimes, on longer runs a small diameter tube decreases air flow to the skimmer.

You could see if the house air is relatively high in CO2 ( the prime suspect for chronically low Ph in tanks with a complete cycle) by taking a water sample ;aerating it in the house for a few minutes and testing the pH; then, take it ouside and aerate it again and test the pH.

It's possible some die off is still occurring after 2 months and bacterial activity is contributing to the issue.

 

[paulsvang]

tmx,

The outside air tube I used was a 1/2" size and my tank is next to the window so i just stuck the end of the tune out the window. The other end went to the venturi inlet of the skimmer. I'll give the water test a try to see if it makes a difference in terms of ph.

Paul

 

[dkeller_nc]

The pH test that Tom describes is a key indicator; if it doesn't change substantially after being aerated outside for 5 to 10 minutes, then I'd suspect you've a buildup of DOC that's depressing your pH. Running a fair amount of GAC will help, as will large water changes.

 

[bertoni]

I agree that the aeration test should give us more information. You could consider running a fan in the window, pointed at the tank, if the temperature is reasonable where you're living. That should raise the pH within a day.

 

[paulsvang]

It would be too cold to leave the window open with a fan blowing in. I'm going to try with a cup of the tank water with a bubbler on it. 10 minutes indoor vs 10 minutes outdoor.

 

[bertoni]

The aeration test takes about three hours total. I'd give it longer than 10 minutes, but that might be enough to get an idea of what's happening.

 

[paulsvang]

I'll leave it out for a couple of hours and see if pH increases.

 

[dkeller_nc]

I'll leave it out for a couple of hours and see if pH increases.

I'd check it after 10 minutes. Gas exchange with aeration in a small volume is very rapid, as is the re-equilibration reaction between carbon dioxide, carbonate, and bicarbonate. The complication with interpreting a 2-3 hour aeration test in a small volume is that evaporation can have a significant effect. Temperature differences between the sample and the calibration temperature of the pH probe also has an influence, though to a lesser extent.

 

[tmz]

I'd also check the venturi for any precipitant clogging the pinhole, restricting airflow to the skimmer. It can be cleaned with a little vinegar. This is usually indicated by less bubbles. Less bubbles equals less actual protein skimming and less gas exchange .

FWIW,I use diy CO2 scrubbers with soda lime from an on line provider,( it's much cheaper than stuff packaged for the hobby and is widely used in rebreathing devices for divers and in anesthesia applications),on my two skimmers and get a bump of around .15 to .2 pH units with them. The run for fresh air in my case would be about 20 feet.

 

[paulsvang]

pH level is still the same after 3 hours sitting outside with the air bubbler in the tank sample water. FYI - Skimmer works fine. I'm at lost. I'll probably just have to do more water changes.

 

[tmz]

It seems odd that after aeration at atmospheric CO2 levels it didn't rise .NSW runs around 8.1 with alk around onlyu 7dkh. Electrical interference may throw the test off if you are testing the outside water and the tank water with the probe and monitor in the same location and the newly mixed water elsewhere.

 

[bertoni]

My guess is that you're seeing a measurement problem. I would get a second opinion on the alkalinity and the pH measurements. If the alkalinity is very low, that could cause this problem. You could check the pH of some freshly-mixed saltwater, as well. If that's aerated outside, it should be well over 8 for pH.

 

[tmz]

The alk measures 9 dkh ,correct?

 

[paulsvang]

Yes. 9 dkh

The freshly mixed salt is at 8.2pH

I'm testing all the water samples in the garage. The mixing saltwater is in the garage. The tank is in the living room. I'm still puzzled.

 

[dkeller_nc]

Presuming that your specific gravity, alkalinity and pH measurements are all correct, I'd suggest running some high-quality GAC. A reactor is optimal for this purpose, but a mesh bag placed in a high-flow area will work. The GAC is easy and has no downsides as long as the dust is rinsed out of it.

In my systems, I typically see a pH rise of 0.1-0.2 when I change the GAC carbon out. The effect lasts about a week in a heavily fed, 50 gallon tank, and I run about 1 cup of BRS ROX carbon in a TLF phosban reactor.