Dose BRS Mag mix cause high Alk?

[AdamNC]

These past weeks I've been doing really good with keeping my Alk steady between 8.4-9.5 dKH. Yesterday I had to dose 65mL of BRS Mag Chloride/Sulfate mix and today did my Alk test and it tested at 11.2 dKH. I wanted to bring my Mag up to 1300ppm. I have my Alk and Ca running off 2 BRS 1.1mL dosing pumps set to dose Alk 3 times a day for 5 mins and Ca 4 times a day at 5 mins. I haven't added anything or changed anything since testing Alk 4 days ago except for the BRS Mag mix. Any ideas? I unplugged my Alk doser to let it come down some.

 

[GainesvilleReef]

You sure you did not get something mixed up? 65 ml of BRS alk would put you right there.

 

[AdamNC]

Absolutely sure I didn't do a mix up. I have 3 1-gallon water jugs. 1 for Alk, 1 for Ca and 1 for Mag. The Alk and Ca jugs are underneath the stand with dosing tubes stuck in them and the Mag jug is on a shelf to the side of the tank. And each jug is labeled with a name tape and black marker. Yea it's perplexing to me too how the Alk shot up.

 

[GainesvilleReef]

When I first got my BRS kit. I noticed it was a lot of white powder and clear liquid in identical jugs. I bought a label maker.

How are you controlling your dosing pumps?

 

[GainesvilleReef]

In a small tank like that it could be from water changes as well.

 

[AdamNC]

In a small tank like that it could be from water changes as well.

hmm never thought of that, I did do a water change on Saturday. I usually buy my water premixed from my LFS and they use Salinity.

All my BRS stuff is in granular form, I had to mix it into separate jugs and they are each separately controlled by a digital timer but the Mag is not on any auto doser.

 

[GainesvilleReef]

I usually keep my water changes less than 5% to avoid alk spikes. I do 10% in my 29 but its an LPS and softy tank and I don't do any dosing at all on it. How often do you test your alk level? Sometimes it can swing on you just because coraline or corals are not growing as fast at that time. I have to back down every now and again on my other tanks.

 

[AdamNC]

About every 2 weeks I do 5 gallons. 29 gallon tank less the rocks/sand I initially filled it with exactly 20 gallons. Never had any issues before. I'm gonna take a guess and say that the mix was probably too high in Alk from the LFS. But usually they are really good at the mixing. I think Salinity runs at 9-10dKH out of the tub?

 

[Randy Holmes-Farley Verified Community Expert]

FWIW, the magnesium additive won't impact alkalinity directly. It may slow the precipitation of calcium carbonate on pumps and such, but i expect that is a small effect.