Dosed Boron, but ICP still reads low?

[Exus]

So on 2/9/2026 I did a Reef-Labs ICP where it said my Boron was 1.775 mg/L, so I dosed enough Captiv8 Boron to increase levels to 4.0 mg/L over the course of a couple weeks on a doser. But my recent ICP on 5/19/2026, it says my boron is only at 2.387 mg/L.

I'm pretty sure I didn't miscalculate the dosage formula on the bottle.

Is it possible for the 4.0 mg/L to get depleted down to 2.387 mg/L in 3 months? Precipitation maybe? Or maybe the concentration of the bottle is off?

I read boron supposedly doesn't matter, but I'm trying to figure out where it could have gone to.

 

[Randy Holmes-Farley Verified Community Expert]

It’s possible it was depleted, yes. A small amount of borate gets incorporated into coral skeletons and abiotic precipitation of calcium carbonate in place of some of the carbonate.

How are you supplementing calcium and alkalinity? Some contain boron and some do not.

It is also possible the additive was off. Are you doing water changes? Maybe the mix is low.

 

[Exus]

It’s possible it was depleted, yes. A small amount of borate gets incorporated into coral skeletons and abiotic precipitation of calcium carbonate in place of some of the carbonate.

How are you supplementing calcium and alkalinity? Some contain boron and some do not.

It is also possible the additive was off. Are you doing water changes? Maybe the mix is low.

I'm dosing All for Reef and carbon dosing with no water changes.

I only export water through skimmate and when flushing media like gfo and activated carbon. I typically add a cup of new salt a month to make up the difference in my 150 gal tank. I only export water through skimmate and when flushing media like gfo and activated carbon. I use instant ocean purple bucket. I typically add a cup of new salt a month to make up the difference in my 150 gal tank. It is a mixed reef with no sps.

 

[Randy Holmes-Farley Verified Community Expert]

Ok, that suggests that the AFR is not keeping up with demand.