Excessive pH & how to deal with it

[Oropher]

Hi folks.

I have a pico 24L aio saltwater tank with no fish, just a bunch of rocks and a tuxedo urchin. I have an external HOB skimmer and a little wave maker. I use RO water (TDS 4ppm) and marine saltmix. Normally I do 10% WC every week.

I'm in the process of making all rocks covered with coralline algae while keeping tank fallow after "suspecting a WS" on my chromis. That fish is now in hypo QT.

I always keep my DT's SG at 1.025, temperature is around 29-30ºC (don't have a fan or chiller), however my pH tends to rise above 8.4. Mg is at 1350, Ca 450, and KH 8.5. Normally I do my reading/test around 8-9 am.

What make my tank's pH keep going up? And how to deal with it.
Thanks folks.

Cheers.

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[jamie1981]

It's impossible for ph to rise to dangerous levels on it's own. Are you dosing anything to the tank?

The only other thing that could cause it to rise is uncured made made rock.

I would bet that your probe is bad or needs to be calibrated.

Don't chase pH

 

[bertoni]

I agree that pH measurement problems are common enough that I'd start there. Cleaning, calibration, and checking for electrical interference all might be useful.

What is being dosed into the tank? Limewater and high-pH alkalinity additives sometimes can raise pH a bit too high. Also, I'd make sure that the water surface has a good rippling motion, to keep aeration up. Photosynthesis can consume carbon dioxide from the water column, which will raise the pH.

 

[Oropher]

2 weeks ato i dosed:
14g MgCl2
3.3g CaCl2
1.4g Na2CO3

May be i need to recalibrate pH meter. 2 weeks ago it has been calibrated with buffer pH4 and 6.86.

There's not much surface ripple as the wave maker direction is more to tilt down. I'm changing direction to more horizontal now to make more ripple.

I use all live rocks but maybe not enough curing time only 10 days. Because I was worried all purple turned white.

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[bertoni]

Two weeks isn't very long. I might clean it, though, just in case. Electrical interference can be an issue, though. I might move the meter to a different circuit and measure a cup of tank water well away from the tank. More aeration might help, too.