Alk drop

Duberz · Feb 3, 2016

My alk last night was 8.232. Tonight it is 7.784. I'm using a Hannah checker. I'm dosing kalk via ato at 1tsp/gal. If I go to 2tsp/gal would that stop the drop? Tank is about 2.5 months old with a few sps,lps and zoa frags. Fwiw all frags are doing well except my rainbow monti that has not extended since I started the kalk last week.

ritter6788 · Feb 3, 2016

Thats not much of a drop. Could vary that much test to test. I'd stick with the testing and watch for further drops. Any additional dosing you do should be small and slow.

Lenny_S · Feb 3, 2016

It's possible the test is just bad. There is a current thread on bad Hanna Alk reagents https://www.reef2reef.com/threads/check-your-hanna-reagent-now.232262/
A .5 dKH drop in 24 hours seems a little odd to me. I have 5 Hammer colonies, 2 Trumpet colonies, a large Duncan colony, 4 medium size SPS colonies, 6 large frags and another 10 smaller frags in a 160 gallon tank. It takes a week for my tank to loose that much Alk.

Duberz · Feb 3, 2016

I checked my reagent against the bad batch and I'm good.

Lenny_S · Feb 3, 2016

I just looked at the specs for the Hanna marine alkalinity colorimeter and in that range its accuracy is only plus or minus 5%. So if you're reading between 145 and 135 ppm that is a 6-7 ppm margin of error. I'm afraid it seems with those checkers your Alk could have been exactly the same for both those tests and still gotten those 2 different readings.
@ritter6788 is right, with that Hanna checker it could just be variation between tests.

Randy Holmes-Farley · Feb 4, 2016

Duberz said:
My alk last night was 8.232. Tonight it is 7.784. I'm using a Hannah checker. I'm dosing kalk via ato at 1tsp/gal. If I go to 2tsp/gal would that stop the drop? Tank is about 2.5 months old with a few sps,lps and zoa frags. Fwiw all frags are doing well except my rainbow monti that has not extended since I started the kalk last week.

I'd be hesitant to say that you for sure have that exact demand (0.45 dKH) based on only one day of demand, but in terms of limewater (kalkwasser), it will take an extra 0.8% of the tank water volume of limewater with 1 tsp per gallon or half that for 2 tsp per gallon to make up the demand. So that is an extra 0.8 gallons of 1 tsp per gallon limewater, or taking 0.8 gallons per day and jumping it from 1 tsp per gallon to 2 tsp per gallon.

That is just an estimate because the higher pH will likely spur demand, so you may need a bit more than the simple math suggests.