Empty tank, alk dropping

[Detroit_aqua]

Hi all. So my tank is about 2.5 months old. After cycling, I partially stocked it with 2 baby tang, 6 juvi chromis, and about 4 other small fish. There have been no fish deaths. I've transferred over some zoas, 2 small lps frags and a single 1" acro frag as testers. In the midst of a heavy initial diatom bloom with some green dust algae also appearing on the rocks, neither of which concern me as apart of a new tank.

Water volume: 180gal
PH (currently): 8.42
Salinity: 1.25
Temp: 78
Alk: 7.68
CA: 442
MG: 1250
Phos: 0.12
Nitrate: 5ppm

Testing via Apex and Trident, probes calibrated within the last 30 days.

Salt mix: Tropic Marin Syn-Biotic (mixes to about 8.5alk)

The issue I'm having is that as of Thursday night last week, the PH has been spiking throughout the day (8.45-8.75 on the worst day) and the alk started falling. The PH has a steady climb from when I turn the lights on until when the lights start dimming, peaking at around 8 pm. 2 days ago I hit the highest peak, which was 8.8, but above 8.5 has not been uncommon. On top of that, my alk is falling. As I said, I have only 3 small stony coral frags in there. I seeded with coralline about a week ago but there is no sign of it yet (as expected).

3 days ago I started up my dos since I saw my alk dropping, but as soon as I dose alk it percipitates into white chunky flakes and just floats around the sump. 2 days ago I turned off the dos. I had started out dosing just 15mls of alk and cal to get a feel for what I needed to dose...up to 60mls alk had no effect on the actual levels of the tank, they kept falling.

The PH spikes started as soon as I fired up my refugium with a small mass of chaeto from algae barn (dosed with a very small bottle of fritz turbo start to help seed new bio media in the fuge). I initially started with 12 hours on for the fuge opposite cycle as my display lights, but after the PH spikes, dropped to 6.

I've tried areating the water via increasing skimmer airflow and pointing return nozzles at the surface, seemed to worsen the PH situation so I stopped.

In short, over the last 24 hours my tank consumed 0.4dkh with only 3 stony frags in the tank, and all attempts to dose result in flaky white alk solution in my sump.

Suggestions to remedy? Any idea what's causing this?

I come from the planted tank world, is it possible the Algae is stripping the water of CO2 and causing the PH to spike? May explain why it happens with lights on.

Thanks for reading!

 

[Detroit_aqua]

Bump

 

[Randy Holmes-Farley Verified Community Expert]

pH 8.55 is OK. Higher pH than that is a problem to the extent that it will accelerate abiotic precipitation of calcium carbonate.

But I suspect the pH may not be as high as you think. maintaining high pH is not easy as aeration brings it down, and most reef tanks are well aerated.

If more aeration worsened the problem, the pH is definitely lower than you think.

Try recalibrating your pH meter.

 

[Detroit_aqua]

pH 8.55 is OK. Higher pH than that is a problem to the extent that it will accelerate abiotic precipitation of calcium carbonate.

But I suspect the pH may not be as high as you think. maintaining high pH is not easy as aeration brings it down, and most reef tanks are well aerated.

If more aeration worsened the problem, the pH is definitely lower than you think.

Try recalibrating your pH meter.

My PH is currently sitting at 8.4 according to both my probe after calibration as well as an api test kit, and LFS test kit. The problem is that I took the water for testing after probe was already reading 8.4 once the ph dropped. For now though, after three days of apparent big swings, it seems stable.

My main concern is why my alk (and now calcium) is dropping when I only have the few small frags in the tank.

Thanks a ton for your response and help with the @Randy Holmes-Farley . The guy at the LFS, while knowledgeable, did not have an answer to this question and I'm scratching my head as well.

 

[Randy Holmes-Farley Verified Community Expert]

Even at pH 8.4, if the alk is below 10 dKH, the pH will drop with aeration. if it does not, the pH is wrong.

There are lots of ways and reasons alkalinity drops, and tons of organisms that use it for calcification. A number of folks also discover they are not dosing as much as they thought.

The white precipitate is likely magnesium hydroxide that should dissolve back in on mixing, but it sounds like you are not adding it to a high enough turbulence area. If it collects somewhere, the local high pH may have time to precipitate calcium carbonate, which will not redissolve

One option is to switch to baking soda since it, as a low pH additive, does not cause that local precipitation.

More dilution of the alk additive and higher flow will also reduce it.

 

[Detroit_aqua]

Even at pH 8.4, if the alk is below 10 dKH, the pH will drop with aeration. if it does not, the pH is wrong.

There are lots of ways and reasons alkalinity drops, and tons of organisms that use it for calcification. A number of folks also discover they are not dosing as much as they thought.

The white precipitate is likely magnesium hydroxide that should dissolve back in on mixing, but it sounds like you are not adding it to a high enough turbulence area. If it collects somewhere, the local high pH may have time to precipitate calcium carbonate, which will not redissolve

One option is to switch to baking soda since it, as a low pH additive, does not cause that local precipitation.

More dilution of the alk additive and higher flow will also reduce it.

Okay! I've started by adding a powerhead below my dosing lines and diluting the mixture further. Hopefully this alleviates the issue. Your insight is greatly appreciated my friend. Will keep you posted

 

[AquaVivaCoral]

Your tank is really young it's not ideal to keep SPS just yet or the parameters spot-on ...

Don't worry a lot about your pH, maybe you just open your window. You have reached the saturation point in the solution I think, if you want to raise alkalinity raise your Mg too or just make some water change, the alk drop can be caused by coralline growth, it consume a lot of stuff from the water or it just precipitate from the water... If Ca is around 450 you need to adjust Mg to 1350 from 1250 - but I always prefer just to make water changes, also check your fresh saltwater mix parameters.
One more thing can contribute to high pH, bacterial bloom can cause a serious lack of oxygen, if your water is cloudy maybe its bacteria.
Anyway your tank is relay young, be patient it will matures and stops giving surprises I hope it helps...