What causes alk consumption to decrease?

zack801 · Mar 21, 2018

I’ve had some weirdness lately where I’m not changing lighting or anything yet my alkalinity consumption seems to go down. I would be dosing the exact same amount at the same times for weeks when all of a sudden my alk starts to climb? Anyone else have this issue? It keeps me paranoid so I usually text daily but I’d love for it to stay more stable. The only thing that I can think of that has changed is my phosphates have gone from .02 to .12 due to my rowaphos being exhausted I believe. Could this change be a cause?

Randy Holmes-Farley · Mar 21, 2018

What are you dosing and how big of an effect are we talking about?

Has the dosing routine change in any way (time of day? times per day?)

Many things can cause reduced demand, some of which you may not even be monitoring.

Lower pH will reduce demand, as will lower starting alkalinity.

Lack of adequate nutrients (are you monitoring nitrate?).

Even possibly less abiotic precipitation of calcium carbonate on or downstream of old GFO compared to newer GFO.

zack801 · Mar 22, 2018

I have been dosing 33ml of reef fusion for alkalinity spread through the day. I noticed my alk consumption was higher it seemed during the peak lighting intensity hours so I dose a little higher from 12-4pm.

This routine has been the same for about a month since it seemed to be dialed in.

I’ve been testing and dosing nitrate for the last couple of months using sodium nitrate. My system does not have detectable nitrate unless I do. I keep it around 2-4ppm

Something I read yesterday in a few places suggested that rowaphos could be absorbing the alk. Since my rowaphos was just exhausted this week and I saw my phosphates start to go up maybe there’s something to that? I just replaced it yesterday

Randy Holmes-Farley · Mar 22, 2018

What size tank?

zack801 · Mar 22, 2018

It’s a 45g with another 10-15g in the sump

Randy Holmes-Farley · Mar 23, 2018

That 33 mL is then a bit over 2 dKH per day. Depending on what is in the tank, and how old it is, it may be that you are getting less abiotic precipitation on rock and sand surfaces as they have become coated with things like organic matter.

zack801 · Mar 23, 2018

The tank is a year old, bare bottom mixed reef but moving more toward sps now. I’ve got coraline covering everything I’m not sure how much alk is used by that. I’ve got a couple colonies of birdsnest and a nice sized tri color colony. Most of the rest are frags that have been added over the last couple of months. I’ve adjusted my alk down to 22ml/day and it’s still not completely leveled out.