sudden kalk and alk drop


you cant buy blue fingers
Premium Member
09/03 bought a new 150 watt 10000k mh for my 29 gallon. added to 4x36 wattpc 50/50
10/03 Alk 3.47 meq/l calc 500ppm
15/03 alk 3.09 meq/l calc 420 ppm

added 10 mll seachem 8.3 buffer 14/03.

My calc and alk have been high for weeks both coming down slowly 20-30 ppm calc per week

are the huge drops due to the mh allowing the reefbuilders (1 sps and 2 lps plus snails etc.) and coralline to really get going.?

Anyway added 10 ml of c balance a and b and will test for changes tomorrow



New member
I'm definately no expert here, but I could easily believe that your coraline going nuts could drop your calcium.

Randy Holmes-Farley

Reef Chemist
Premium Member
Calcium dropping 80 ppm in 5 days is not unreasonable or atypical, although it is on the middle to high end of normal. That would be the same as if one were maintaining calcium with 2% of the tank volume added each day in saturated limewater.

There may also be a fair amount of uncertainty in the size of that drop as calcium kits may not be as accurate as folks often assume. :)


you cant buy blue fingers
Premium Member
so I started by the new regime of dosing cbalance kast night and tested the water again tonight.

I addaed 10ml of each to my 29 gallon tank and tested exactly 24 hrs later.

Alk rose from 3.09 to 3.15 meq
calc rose form 420 to 440 ppm.

I am fairly happy with those figures so i added 10ml more of each and will test each day until I get the same readings ie 3.15 and 440.
If it takes two days then I will know that 10 ml every two days will hold the levels stable.

does this sound like a plan for now

Thanks again


you cant buy blue fingers
Premium Member
Hello again
so I dosed the tank with 10ml A and B for the past 3 days.
The results were
Calc 440ppm holding steady
Alk 2.97 dropping
I know organisism take up alk more readily than calc so
last night I added the 10ml dose of each A AND B and 5ml of the seachem buffer liquid "Safely raises and maintains ph at 8.3 and raises alk". i KNOW i COULD HAVE JUST ADDED PART b BUT i DONT WANT TO UNBALANCE THE AMONTS i HAVE AND WANT TO USE up the sea chem buffer.
Any probs with this?

Also I just set up a swanky new kalwasser top up system at the minute it only has ro in it
Which kalkwasser mix is good? and what implications will it have on the dosing of the two part?

Again thanks you are the most helpful person in the reef chemistry world!!

Randy Holmes-Farley

Reef Chemist
Premium Member
I would stick to dosing equal parts unless things get way out of line (which they are not). The two part has the right ratio of calcium and alkalinity to offset calcification loses (18-20 ppm calcium for each 1 meq/L (2.8 dKH) of alkalinity).

Any brand of food grade lime is OK. This article has more on lime grades:

What Your Grandmother Never Told You About Lime

thanks you are the most helpful person in the reef chemistry world!!

You're welcome and thanks. :)