Alkalinity demand increased with pH increased.

Agrass1992 · Jul 5, 2021

Hello everyone, quick question/ recording of observations. I recently added a co2 reactor to my 180 gallon reef tank. I use an Apex and have been observing some swings from 7.8 down to 7.5 or sometimes lower. The co2 reactor did exactly what I had hoped it would do. It increased my ph to 8.30 during the peak and it drops to 8.15 or so later. I know this range can increase coral growth, according to various BRS videos. I have noticed my alkalinity demand nearly double since that time. I use instant ocean reef crystals and the calcium mixes pretty high so I only dos alkalinity at this time. I previously only needed about 10 to 20ml per day, split up among 4 intervals, to maintain or slowly decrease my alk, which is usually around 8.5 dkh. Now I'm struggling to stay ahead of the curve. I have increased to 36ml per day, waiting for my next trident reading to see if the new interval of 9ml over 6 hours keeps it steady or it drops again.

Also I'd say I have a medium to lightly stocked tank. One decent sized elegance, about 10 or so hammer coral heads among different colonies, a few different acans, on duncan with about a dozen heads and one torch.

Has anyone else experienced something similar when increasing their pH?

ADAM · Jul 5, 2021

Sounds about right. They’re happier so they’re consuming more. Once I got my pH to stay above 8.1 all day I saw a big increase in consumption.

But if ALK is being consumed it’s definitely using calcium, and other elements also. I have a trident also and the B and C test I mainly only use to see if they’re trending one way or another whereas I base ALL dosing on test A (ALK)

Now that pH is stable I find my ALK consumption is slowed if PO4 starts to creep up when it’s time to change out my rowaphos. Pretty easy reminder if I get slack or forget on maintenance day.