View Full Version : Alk question

06/26/2010, 10:36 PM
ive been trying to get a straight answer to this question but no one seems to know so i suppose ill ask again. my alk seems high 11.4 dkh i was using oceanic salt and now im back to RC and im hoping it will go down to where i want it 9-10 dkh. im not dosing it but i have been dosing mag and Ca to get the levels up. will dosing ca and mag bring up alk? and is there any other method to lowering it besides water changes and letting the corals use it? thankfully i got my Mag and Ca where i want them so i can stop dosing. thanks for suggestions

06/27/2010, 05:35 AM
Have you been dosing alk in the past?

Both of the salt mixes should not need to be supplemented for calcium and mag. if you did not dose any alk, as they are both quite high in calcium and mag. Mag is used quite slowly in comparison to the other two. A reef tank will use only about 7 ppm calcium for every 1 dKH of alk used. This may mean you have test kit problems, if so.

The results below are what Billy found for your salt mixes at a salinity of 1.0264 using a properly calibrated refractometer:

calcium: 580
alk: 8.5
mag: 1650

Reef Crystals (new)
calcium: 490
alk: 13
mag: 1440

06/27/2010, 10:20 AM
Dosing magnesium(Mg++) and calcium(Ca++) will not directly increase alkalinity . However, higher magnesium levels will slow the precipitation of calcium carbonate which is the union of calcium(Ca++ and carbonate (C03) ions, thus allowing the water to hold more calcium and alkalinity in solution.

06/27/2010, 09:15 PM
If the calcium and magnesium were in the reasonable zone before dosing, adding them will not affect alkalinity measurably. What were the levels before and after dosing?

In any case, Tom is correct, and dosing them will not directly add alkalinity or change the level.

06/28/2010, 09:25 AM
ok thanks for the help guys!! during the tank switch i used petco salt which i was told is a oceanic type. but im not sure it is also in my previous 55 i never dosed and during the tank swap things got even more outa wack. heres the levels when i started
365 ca, 1100 mag, and 10.2 alk. it took a little while to figure out how to dose as its the first time ive done it. so it took me almost a month to get to where i am now. on a side note besides the high alk the petco salt hasn't stressed any of my high end sps frags after water changes and 24 hour mature.

06/28/2010, 02:09 PM
The numbers are reasonable, and you can increase the alkalinity and magnesium to higher levels if you want. As long as the changes are fairly gradual, the tank should be fine, and the dosing won't change alkalinity. I would target 100 ppm per day of calcium or 100 ppm per day of magnesium, at most, and probably dose only 50 ppm of each if I wanted to dose them at the same time, just to be cautious. The supplements will have some contaminants, and keeping the daily contaminant dosing down is a good idea.

06/28/2010, 02:32 PM
oohh no those where my measurements almost a month ago heres my most recent
ca 425
alk in dkh 11.4
mag 1410
with salifert

06/28/2010, 03:23 PM
Oh, okay. The new numbers are fine, too. :)

06/28/2010, 05:41 PM
so is that high a alk something to worry about even or should i try to get it lower?

06/28/2010, 05:56 PM
That alkalinity level should be fine unless you're dosing carbon. Some people who dose carbon seem to have problems with the alkalinity that high. On the other hand, some people dose carbon and run with alkalinity at 11 dKH without issues.

06/28/2010, 09:34 PM
do you mean like vodka dosing or running granular carbon? i run the BRS reactor with the ROX 8 stuff and GFO but no vodka. also on a side note can you run gfo carbon and vodka dose? thanks again bertoni :D

06/29/2010, 02:52 PM
Sorry, I meant vodka dosing, or any of the similar approaches. :) As far as I'm aware, there's no problem with combining carbon and vodka dosing.

06/29/2010, 11:49 PM
I tested freshly mixed Oceanic @ 1.025 and the KH was at 10.4 Is this the regular KH i can exspect with this brand salt mix? As i am i Coralife user but have been told they are all made by the same Co now and I'm seeing Sludge with the Coralife that I never saw B4? Just curious???

06/30/2010, 06:22 AM
I use Oceanic and it is always around 8-9 for me. I am on my 4th 200 gal bucket.