2-Part Dosing question, Can I dose Only Alk & Mag?

[bo0sted2g]

I thought I read some where that when dosing 2-part that you should always dose both parts......

My question is my Calcium is at 450
But my Alk is at 6.8.
Mag is at 1200

I just got my 2-part total package from BRS and am wondering for the initial dose should I just dose Alk and Mag solutions until they are at the desired levels? and leave the calcium alone for now?
(I know I should only raise the Mag 100ppm per day and Alk no more than 1.4)

I don't have many corals at this point just some GSP, a 4 headed frag of duncan and a candy cane with 6 heads. But my duncan has not opened more than 1/4th of the way in the 2 weeks that Ihave had him. and the candy cane was doing great until a snail knocked him down into the sand and is now slowly dying. Im assuming they are not happy with the low Alk levels so i would like to boost it up and see if they will come back in all their glory.

Other parameters are
Temp - 78.8
SG- 1.025
Amm-0
Trite-0
Trate-0
PH-8.2
Cal-450
Alk-6.6
Mag-1200

 

[wkscott]

Never dose what you don't need. If your sslt gives you enough calcium, don't add any more. As your tank matures, test, and only add what you meed.

 

[p7willm]

Most of the time when something uses Alk or Ca it uses about the same amount of both. In the beginning my Alk was lower than my Ca so I dosed more Alk. Now that they are in balance and my tank has had longer to mature I am using both about the same.

 

[Randy Holmes-Farley]

So let's back up and actually consider what would happen if you did follow the actual advice to dose equally to maintain alkalinity.

Let's assume your alkalinity target is 8 dKH.

WOW, I don't want to use both equally because calcium is already 450 ppm. Right?

Nonsense.

If you use a quality two part to boost alk from 6.8 to 8 dKH (1.2 dKH), what happens to calcium?

The two part should add about 8 ppm calcium.

You won't even be able to detect that with a typical hobby kit, but even so, it boosts calcium from 450 to 458 ppm. That is no concern whatsoever.

So unless calcium is already too high (say, above 550 ppm) there's never a strong case for dosing unevenly to maintain alkalintuy.

That said, Of course you can make a one time correction to alkalinity and not calcium using just the alk part. Since your salt mix may be imbalanced relative to the tank, you might find you want to occasionally make such corrections.

Finally, magnesium should always be corrected independently of determining a two part dose, and the optimal supplement recipe is different for making such a correction (although you can likely use the two part magnesium portion for make the correction without apparent tank problem). Two parts maintain magnesium where it is and won't (can't) be used to raise magnesium when dosing all the parts at specified rates to maintain alkalinity.

 

[Randy Holmes-Farley]

Never dose what you don't need. If your sslt gives you enough calcium, don't add any more. As your tank matures, test, and only add what you meed.

IMO, dosing the two part equally all the time to maintain alkalinity is a better approach for most hobbyists than continually tweaking the doses.

 

[bo0sted2g]

So I followed the mixing instructions and the dosing instructions for the BRS ingredients I got using their calculator on the website........ and It says not to raise the DKH more than 1.4 per day. I mixed all the solutions as directed and the only thing I can think of where I went wrong here could be my estimate of total tank volume. But I added the dose calculated by the calculator and ended up going from 6.8 to 11.6. So lesson learned start small and test between!

How severe will this impact be from going up almost double the alkalinity? I have some fresh salt water already mixed up and would just have to throw the heater in it for a bit and then could change some water out if needed.

 

[Randy Holmes-Farley]

I wouldn't do a special large water change. I'd just let it fall on its own (assuming the value is real; have you used this kit a lot to be sure of using it correctly?).

Your total water volume won't be off by more than a factor of 2 if you simply assume all your tank is water volume (90 gallon tank = 90 gallon water volume).

I think there may be some other error. Maybe in mixing, measuring the dose, or in testing.