Still having alk problems

Duberz · Feb 10, 2016

My alk is still dropping daily. I'm up to fully saturated(2tsp/gal) in my ato. My readings yesterday were.
Alk 7.56
Cal 425
Mag 1300
Ph 8.3
Sal 1.025
Today everything is exactly the same but alk dropped to 7.28. It drops every day but all other parameters stay constant. I have been dosing the alk up to 9 but it just keeps falling back down even with the kalk. There is only about 7 frags and no coralline. Any idea what's going on or what can I do to keep my alk around 9?

AllSignsPointToFish · Feb 10, 2016

I hear your pain, but I have the opposite problem. I can't seem to get calcium levels up, even with I use limewater to top off. Calcium is always around 400ppm, but when I use limewater top off, the alkalinity shoots to 11+. Magnesium levels are consistently above 1400 ppm, so low magnesium can't be the problem.

Randy Holmes-Farley · Feb 11, 2016

AllSignsPointToFIsh said:
I hear your pain, but I have the opposite problem. I can't seem to get calcium levels up, even with I use limewater to top off. Calcium is always around 400ppm, but when I use limewater top off, the alkalinity shoots to 11+. Magnesium levels are consistently above 1400 ppm, so low magnesium can't be the problem.

Magnesium at any level would not explain that, but simple math does.

L:imewater adds 20 ppm of calcium for each 1 meq/L (2.8 dKH) of alkalinity.

So for a 40 ppm boost to calcium using limewater, alk must jump by 2 meq/L or 5.6 dKH.

Consequently, limewater is not suitable for large boosts to calcium, only for maintaining it against calcification losses, which are also at a similar ratio.

For boosting calcium levels substantially without any rise to alkalinity, calcium chloride is the best product.

Duberz · Feb 11, 2016

Randy what would you suggest I do in my case?

Randy Holmes-Farley · Feb 11, 2016

Sorry, I got distracted by the second post.

When limewter cannot keep up with alkalinity demand (as often happens in SPS tanks), I'd look to use a two part in addition to, or instead of, the limewater.

You can use a two part like B-ionic or a DIY using ingredients from a place like BRS or Dr Foster and Smith.

Dose enough of both parts of the two part equally to maintain the alkalinity where you want it.

Duberz · Feb 11, 2016

Thanks Randy...is it common for a tank with only small frags not allow limewater to hold parameters steady?

Randy Holmes-Farley · Feb 11, 2016

Duberz said:
Thanks Randy...is it common for a tank with only small frags not allow limewater to hold parameters steady?

It depends on the evaporation rate.

Adding 1.25% of the total water volume each day in saturated limewater adds about 0.5 meq/L (1.4 dKH) of alkalinity. That's not enough for many tanks if evaporation is low.

That said, I use just limewater for my system (not an SPS tank).