View Full Version : Ca/Alk driving me crazy

12/21/2006, 11:52 PM
The Ca/Alk issues are driving me crazy - I just can not seem to get my Ca down and Alk up.

15 month old 140g tank. Using Kalk reactor that stirs once a day - supplies all top off water. Ca reactor also installed. Medium SPS and LPS in tank.

All test kits used are Salifert

Last week
Temp 79
Alk 5.5 KH
pH 8.1
Ca 540

30% water change. Added 10 tsp baking soda. Turned off Kalk and Ca reactor

two days ago
Temp 79
Alk 7KH
Mag 1050
Ca 540
pH 8.1

Added 5 tsp of Baking soda and 3 cups Epson salt mix

Temp 79
Alk 5.5KH
Ca 540
pH 8.0

Question is - not sure what to do next? Another water change? I hate to add more baking soda.

12/22/2006, 01:32 AM
Your Mg is quite low. I suggest you adding Mg additives.

You turned off Kalk and Ca reactor. So , if you have SPS coral and coral grow fast in your aquarium Ca consumption can be 20ppm daily and balanced KH consumption can be 2,8 daily (based on data for my 130g. reef aquarium).

In such case KH level will decrease for 2,8 every day , if you will not add baking soda. So you have to add baking soda every day.

If you will add today 23g baking soda (5 tsp) KH will increase from 5,5dKH to 8,3dKH and Ca will stay on 540 ppm.

With 20 ppm Ca and balanced alk. consumption, tomorrow you will have

KH = 5,5 and
Ca 520 pp

So, you will add 5 tsp of baking soda again

and again

This is theory, but according to my experineces , it will be very similar in the reality.

12/22/2006, 08:42 AM
I like Bojan's ideas.

My method is:

If ca gets too high, turn off the ca reactor.
alk too low add baked baking soda.

The magnesium is really improtant add mg cl.

Well that is too easy.

12/22/2006, 09:58 AM
I did add Mag but have not test it again. I will continue to add baking soda to see what I get.

12/22/2006, 10:39 AM
<a href=showthread.php?s=&postid=8806494#post8806494 target=_blank>Originally posted</a> by Bojan
... if you will not add baking soda. So you have to add baking soda every day.

I thought a calcium reactor irradicates the need to dose calcium or buffer.

12/22/2006, 03:10 PM
Will I hit a point as to where Ca and Alk will maintain itself with the Kalk reactor and Ca reactor? Or will I need to add baking soda forever?

12/22/2006, 03:26 PM
You likely will be able to tune the reactors so that you won't need to add baking soda.

I'd be careful about using Epsom salts as the only magnesium additive. That approach can lead to elevated sulfate. This article discusses DIY magnesium supplements:


Most of the commercial supplements, except SeaChem, are good as well.

This calculator might help pick doses:


I wouldn't change Ca or Mg by more than 100 ppm per day.

12/23/2006, 11:11 AM
What is wrong with SeaChem?

12/23/2006, 07:00 PM
SeaChem is mostly just Epsom salts, so it throws off the ionic balance.

12/23/2006, 08:02 PM
I have been having the same problem with ALK/DKH. Is it bad to use baking soda everyday? I would like to maintain my dkh around 9 but its 6.4 everyday so I have to raise it. Is this going to be the norm everyday for me? Baking soda on a daily basis?
Sorry for the high jack...............
PS my tank is sps only and 120 gallon cube.
temp 80
ph 8.0
calcium 410
mag 1080
dkh 6.4
PSS Is it a good idea to raise the dkh to 12 with baking sode and when it goes down to 9 bring it back up to 12?

12/23/2006, 09:03 PM
Dosing alkalinity every day is fairly common. I use a 2-part to try to keep the ionic balance in line. I'd limit the alkalinity to 11 dKH or so, though.

The magnesium level is a little low as well. I'd try to get it to 1275 ppm or so. The Kent, ESV, and Warner supplements are okay for this, and there's a DIY recipe as well.

12/23/2006, 09:22 PM
What is considered a low level of sulphate, in reference to the chart?

12/23/2006, 10:18 PM
I'm not sure which chart you mean. The normal level of sulfate is 2700 ppm in saltwater:


12/23/2006, 10:32 PM
Shoot. Sorry, it was actually a chart from an article within the article you posted:

It's the first table (TableI) you see.

12/23/2006, 10:36 PM
I think you're referring to the CoraLife salt, which seems to have had about half the normal amount of sulfur, and thus likely half the normal level of sulfate.