Need to start dosing


New member
I've been noticing my Alk dropping over time regardless of water changes. I've already bought a dosing pump and BRS Kalkwasser and am dosing 1/2 saturation and at a way low dose. My alkalinity is consistently around 7.3 and my calcium is inconsistent (maybe just my testing). Last couple of weeks' results
Alk 8.6 Calc 480
Alk 7.6 Calc 430
Alk 7.4 Calc 440
Alk 7.4 Calc 450
Alk 8.2 Calc 410
Alk 7.8 Calc 460
Alk 7.8 Calc 470
Alk 7.8 Calc 420
Alk 7.3 Calc 450
Alk 7.8 Calc 440
The calculator says if I want to increase Alkalinity from 7.3 to 8.5 would take almost 54 ounces (1600ml) of saturated Kalkwasser solution. Dosing once per hour it would be about 60ml per hour. Does that sound correct? I've been trying to understand this for way too long so thought I would ask for special assistance. :) Thanks in advance


Did you write that down correctly? Your tank would have to be roughly 900 gallons to raise the alkalinity level from 7.3 to 8.5 according to the brs calculator. What size is your tank? Even at a half saturation 1600 ml still seems like a ton.

And I'll run you through what I do for dosing using brs sodium bicarbonate and calcium chloride. I have a 75 gallon sps dominated tank. When I noticed my alkalinity dropping I started measuring it every two days. After a week I was able to figure out how much to dose daily so that it remained constant. My total system volume is about 85 gallons. My alkalinity drops about 0.6-0.7 daily which is roughly 80ml of brs sodium bicarbonate. So that is how much I dose each day. I've also found that if I want to raise my alk a significant amount, doing it over a period of a few weeks is best rather than all in one day. Also now that I know how much to dose each day I only measure about once a week and make adjustments if needed. Most of the time it remains constant


Staff member
RC Mod
If I need to adjust alk and cal I use buffer (Kent) and regular calcium over a number of days; THEN keep it there with kalk (Mrs Wages Pickling Lime). DO check your magnesium. !350 is a good reading. If it falls below 1200, your alk will go down, stubbornly so, no matter what you dose.


New member
Thank you both for replying! My tank is a 40 breeder with a 20 gallon sump. I have a ton of live rock so I just use 40g as my volume. Over the weekend, I was able to get my alk from 7.8dKH up to 9dKH using soda ash. I have a mixed reef with several soft corals, several hard corals, one fairly large sps (growing like a weed) and 3 small sps frags. Now, I'd like to keep my alk around 9dKH and my original post is my log of daily alk consumption (seems to sway for some reason in both directions). I'm going to say that its human error on the testing. I'm using Salifert test kits. What would you think a safe starting point would be for dosing BRS kalk (My kalk mix is 1tsp of BRS kalkwasser mixed with 5 quarts of RODI which I think is a fairly weak mix) and I am dosing 6ml/hour. Magnesium is typically around 1290ppm I dose Kent when it drops below 1300ppm. Thanks again I really appreciate the help.