PH jump

[rygh]

I have really noticed a big PH jump when my scrubber kicks on.
It normally jumps about 0.15 or so, but did jump from 8.25 to 8.5 once.
And jumps quickly, like less than half an hour for a 250 gallon tank.
My kH is fairly normal at around 8-9.

Anyone else with a digital ph meter notice similar effects?

Not entirely surprising, since the scrubber is pulling the CO2 out of the water, which raises ph.
But I was surprised by the amount and rate.

I really worry about it stressing the fish and coral, plus at 8.5 or so, calcium starts to precipitate out
a bit, which has been causing issues with my pumps.

I already switched from sodium carbonate to bicarbonate for Alk dosing.
I may have to split the lighting somehow, to only have half on at a time.

[Aeros]

I have a daily PH swing ranging from 8.0 to 8.5. I know it's anecdotal, but everything's doing fine in my system.

That being said: if you would like to narrow you PH swing you have some options.

Run you ATS opposite your display lights minimizing overlap to when you DT lights come on.

Dose you soda ash after your DT lights are off.

Install a fan to blow across a water surface; increasing gas exchange (taking in more CO2 from the atmosphere)

If you have a skimmer with an air line, have it draw it's air from outside if possible. Get X lenth of tube it won't affect the skimming and it will normalize the CO2 with the atmosphere better than a fan.

Open some windows in you home.

Dose with soda (fizzy) water to drop PH.

In regards to Ca percipitation: what do you keep your Ca and KH lvls at?

I ask because I have a hard time maintaining mine (damn coraline sucks it out faster than I can safely add it) and "try to hold at 500ppm @12 KH through daily dosing. I have only seen precipitation while adding Ca to overflow too soon after adding soda ash water. And it just made it snowy. I have never had deposits on equiptmemt; unless you count coraline.

[Rumpy Pumpy]

I have really noticed a big PH jump when my scrubber kicks on.
It normally jumps about 0.15 or so, but did jump from 8.25 to 8.5 once.
And jumps quickly, like less than half an hour for a 250 gallon tank.
My kH is fairly normal at around 8-9.


Do you run it on a partially reverse cycle with the tank lights? (ie, the scubber light are on while the tank lights are off & vice versa)

[rygh]

That is good to hear about not seeing major issues.

I do run reverse cycle already.
Good idea on running skimmer air input outside.

I can switch Alk dosing to only run when scrubber is off. Currently it is a little bit every hour, 24/7.

I had a huge amount of trouble keeping my Ca/Alk up as well when pH was hitting 8.5+.
After the switch to baking soda, and pH dropping, Ca really shot up fast, with no change in dosage.
At high pH, it precipitates out. Not necessarily as snow, but as deposits on everything.
In particular, parts of my sand bed turned to concrete.

I generally run Alk at 8-9, and Ca (now) at 450 or so. Before, it was about 380, and still precipitating out.

I tried a fan a while back. It helped a bit, but evaporation went way up, and heaters were always on.
Now that it is summer, could start it again though.

Along those lines, I was thinking of adding air bubbles to the ATS intake. Not only would it help pH, but
it might even help growth, since it helps supply extra CO2 to the screen.

[Aeros]

@ Rumpy

I've always run reverse as per SMs instructions. I didn't always have a PH probe so I'm sure my swings were much high before my ATS, but who knows.

I did a lot of reading on alk and PH, wetwebmedia is a great source.

Anyway, my swings were caused by poor gas exchange. I have since installed a fan and typical change is now between 8.2 and 8.3 daily.

As for precipitation: Rygh what does your coral stock consist of? Do you have large amounts of coraline?

That is the first time I've heard of sand doing that.

As for bubbles in you ATS intake: that might work. Makes me think of my bubbles and how I hate them getting in the DT.

I might have to try bicarbonate so I can dose more. Maybe 50/50 to cancel out any ph change.

[SantaMonica]

I add a spoon or baking soda as needed. Brings the pH down to normal.

With both scrubbers on, and the limewater dosing, pH can go up forever. I run two pH meters simulaneously.

[rygh]

Just a note that the PH seems to be in control now.
Two key things :
1) Switching from Soda Ash to Baking Soda.
2) Eliminating the small overlap when both display tank and turf scrubber were on.
While I was running counter-cycle, it was not perfectly so, since scrubber lights were
on for a long time. I shortened that. That spike was really big.

BTW: This is gut-feel, hardly measured, but it appears that high PH also slows scrubber growth.
Nothing has changed, other than a slight reduction on time of scrubber lights on, and I appear
to be getting a bit more growth.

[SantaMonica]

it appears that high PH also slows scrubber growth

I'm not to sure about this. Higher pH is known to help precipitate phosphate, which might actually help the algae growth.

What you might be seeing is that by adding baking soda (which reduces pH), you are give more carbon to the algae growth (in the form of bicarbonate).

[rygh]

it appears that high PH also slows scrubber growth

I'm not to sure about this. Higher pH is known to help precipitate phosphate, which might actually help the algae growth.

What you might be seeing is that by adding baking soda (which reduces pH), you are give more carbon to the algae growth (in the form of bicarbonate).

Your first point confuses me. Precipitating phosphate (presumably to calcium phosphate) should mean less phosphate available for algae,
since once precipitated, it is unusable. Thus high pH should reduce algae growth.

[SantaMonica]

Readiness for precipitation also, apparently, makes phosphate easier to "grab" by algae. Seems to be a combination of biological uptake by the algae, and precipitation onto the algal cells, at the same time.