Alkalinity drop when PH goes up

[usfpaul82]

So I wanted to get some opinions on what I am seeing with my Alkalinity and PH. I have a well established 90 gallon, nearly 10 years old. But a few months ago I gave it a major overhaul and removed a lot of corals and started fresh. It is SPS heavy with large frags to small colonies at the moment.

Anyways, my Alk has been steady at around 9 (using Trident) and my PH on the low end about 7.8 - 8 ish. I decided to add a CO2 scrubber and boy did that make a difference in PH. It climbed to 8.25 - 8.35 essentially in 24 hours. The chart below shows my Alk and PH values overlaid. Orange is Alk and Blue is PH. You can see the spike in PH and an exact corresponding drop off in Alkalinity. From what you see, is this an indication of additional alkalinity consumption from my corals due to the higher PH? Seems like a very fast response in alkalinity consumption. I am now tweaking my Alk dosing (2part) to match the new uptake I am seeing. Anything I should be worried about? My calcium level seems to be unaffected as of yet and hold steady at about 450.

 

[homer1475]

Your seeing exactly what you should be seeing with an increase in PH.

Increased PH leads to more uptake by corals which means they grow faster(up to a certain PH, then it declines the higher you get).

Nothing to worry about other then maybe having to prune more often from more growth. Just increase your ALK and CAL dosing to match the consumption from the increased PH.

EDIT:
Keep in mind with more calcareous growth, you need detectable levels of nutrients so you don't end up with burnt tips(calcareous growth but no "skin" on the bone).

 

[usfpaul82]

Your seeing exactly what you should be seeing with an increase in PH.

Increased PH leads to more uptake by corals which means they grow faster(up to a certain PH, then it declines the higher you get).

Nothing to worry about other then maybe having to prune more often from more growth. Just increase your ALK and CAL dosing to match the consumption from the increased PH.

EDIT:
Keep in mind with more calcareous growth, you need detectable levels of nutrients so you don't end up with burnt tips(calcareous growth but no "skin" on the bone).

Thanks! That's what I figured. I was just really surprised to see that happen so quickly, that corals starting up talking additional alk immediately.

 

[Randy Holmes-Farley Verified Community Expert]

Thanks! That's what I figured. I was just really surprised to see that happen so quickly, that corals starting up talking additional alk immediately.

Both abiotic precipitation and organism uptake can playa role and respond rapidly. In fact, one might think corals could overshoot initially, if they are primed to work really hard to take up alk/pump out H+ and it is suddenly easier.

 

[Reefinmike]

Check out my recent experiment with lye. https://www.reef2reef.com/threads/chasing-ph-stability-and-alkalinity-stability.779022/

It’s basically a dosable co2 scrubber and alkalinity additive in one. You have the gear to go down this rabbit hole so it’s something to consider. do your own research, use proper PPE and use layers of redundancy please.

 

[RobB'z Reef]

older post i know but I was researching this EXACT same phenomena. I recently added a refugium on an opposite schedule, got my CO2 scrubbing dialed in with fresh outside air etc. I am only dosing kalk and my alk has been dead steady at 8 for the last 3 months (new tank) and my ph was normally 7.8 to 8 on a good day. Now it's running low of 8.1 at night (refugium is still fairly new) and highs of 8.3+ during the day. My alk tanked to 5.5 in a couple days and i was like double-U-teeF?! this helps explain a lot. Going to slowly dose some soda ash to bring it back inline with the former numbers and then track to see how my consumption has changed.

 

[Semper.Reefing]

Adding to this thread to confirm! I set up a hose running outside for my skimmer intake and leave my ice cap Kalk reactor constantly stirring and reached a higher pH. Immediately saw the drop in alk. Adjusting my soda ash dosing now.

 

[Randy Holmes-Farley Verified Community Expert]

Adding to this thread to confirm! I set up a hose running outside for my skimmer intake and leave my ice cap Kalk reactor constantly stirring and reached a higher pH. Immediately saw the drop in alk. Adjusting my soda ash dosing now.

Thanks for the info. :)