Can't maintain alk...

[andresont]

Originally Posted by MikeP

I've never been able to keep Alk very high in my tank. Over the weekend I did a water change and brought Cal, Mag, and Alk levels up to where they should be. Calcium is at 440, Magnesium is at 1350 and Alk was at 9.8 (I'd like to bump it up a bit more but that seems to be as high as it will go) I tested for Alk yesterday morning (9.8) and then again that night (about 15 hours later) and it was down to 8.4 but other levels were still the same. Why does my Alk drop so fast?

I find it very easy with new salifert two in one KH+PH buffer, i just use a little every time i add water to top up the tank level.
I don’t even test anymore because tests are unreliable anyway.

[ed99]

Originally Posted by untamed

I assume that you are using some sort of balanced Ca/Alk supplement. Generally speaking...if you are measuring low Alk it probably means that you aren't adding enough of the balanced supplement. You might think that more balanced additive would drive BOTH Ca and Alk up...but it doesn't work quite like that.

Another way of saying the same thing...is if you are not adding enough balanced additive (ie: Ca Reacter running to low, or not enough Kalk, or not enough C-Balance etc....), you'll see low Alk before you see low Ca.

I'm adding the Seachem Reef Builder which says it boosts alkalinity. I'm not sure what is in there, though it does mention there is some Ca amongst other cations. I have not seen [Ca] below 400 for months and it has come up t0 425-450 since I've gone hard on the alkalinity (I wasn't testing the alk for ages since I had never had trouble with it before).

If I'm not adding enough of the alk booster should I expect to see an immediate rise followed by the slow decline over the next two days? I don't have any SPS so I wouldn't expect to have such a high alkalinity demand in the tank.

I'm also wondering if I would be better off using washing soda or baking soda to get back to a better ratio of Ca to carbonate?

[MikeP]

It's sounding like it comes down to what you use to dose. I thought maybe it had more to do with other elements in the tank? Should I try to get the alk level up higher (like 11 or 12 dkh) and see how fast it comes down.

[kwirky]

try baked baking soda to raise alk. (sodium bicarbonate anhydroxide)
spread a thin (1/4" layer) of baking soda on a cookie sheet lined with tinfoil. Bake it in the oven at 400F for 2 hours. This drives the co2 out of the baking soda so that idoesn't lower your pH when you add it into the tank. It's ok to cook it at a higher temperature or for longer if you want to be sure.

Then use this calculator here to find out how much to add.

http://reef.diesyst.com/flashcalc/flashcalc.html

Tell it all your levels, your desired level of the parameter you want changed and what you're using to raise it. It'll tell you how much to add to raise your alk, and tell you the ballanced calcium for that alkalinity level.

For instance you have an alk of 7dkH, and you want 8.5dkH. You're using baked baking soda. Your total water volume is 100 gallons. You need to add 10.7 grams of the baked baking soda and your ballanced calcium level would be 420ppm.

(alk dosing should be done gradually to prevent pH spikes. Don't raise your pH more than 0.2 per day)

You'll have to keep on top of your dosing of 2 part afterwards otherwise your levels will just go outa whack again.

And here's an excellent article on making your own 2 part:
http://reefkeeping.com/issues/2006-02/rhf/index.php