Can't keep alkalinity up

Golfman12 · Mar 16, 2015

I have a 4 month old tank that I just cannot keep alkalinity above 6.7 dkh. The tank is a 40 breeder and I keep salinity at 34ppt calcium has been stable around 420, but Mg is getting used very rapidly. I have been dosing using brightwell calcium, alk and mg. I have about 15 stony coral frags. I have slowly increased the dosing amount up to 10 ml in one day of alkalinity but see only a slight change if any at all the next day. I know 6.7 dkh may be close to seawater but I've never kept a tank with low alkalinity, my comfort zone would be around 8-9. Any ideas on what's happening?

JOKER · Mar 16, 2015

I would bet you are seeing a lot of coralline algae which will use up the alk. I would keep up the dosing and maybe increase it a little. I would spread the doses out though. Wait an hour between dosing the alk and calcium.

Reefing Madness · Mar 16, 2015

With Stony corals and coralline, it gets used quickly. What salt are you using? Whats your water change period? Most of the upper Reef brands keep their numbers high, and could help you out in this instance.
Have you tried Randys 2 Part?
An Improved Do-it-Yourself Two-Part Calcium and Alkalinity Supplement System by Randy Holmes-Farley - Reefkeeping.com

Randy Holmes-Farley · Mar 16, 2015

Which Brightwell product?

If it is the Alkaline8.3, 10 mL a day into 40 gallons is only adding 0.8 dKH per day, which isn't that much and adding more may be in order if you want alk higher.

I'd up it to 15 mL per day and see what happens over a few days.

Golfman12 · Mar 16, 2015

Yes I am using the alkaline8.3 and I do a 5 gallon water change weekly with Red Sea coral pro salt. I don't have any visible coraline on my rocks right now so I didn't thing 15 small frags would use up that much. I will try the 15 ml and see if that helps.

Randy Holmes-Farley · Mar 16, 2015

OK, let us know what happens.

FWIW, even some soft corals tanks can use as much as 2-3 dKH per day, which is quite a bit more than you were dosing.

Big Dog · Mar 17, 2015

I have a 180 just over 3 months old with mostly LPS and was experiencing the same thing especially after a coralline outbreak (Calcium at 340 and 5.4 dkh, magnesium has been steady at 1280). Currently dosing Reef Complete and Reef Carbonate, both at 60ml bi-weekly. I've finally have calcium at 420 and alk at 7 dkh. Looking for the climb to continue to find the happy medium but the recent addition of corals may hamper that ...............

Good luck and be diligent with testing in the climb!