Kalkwasser advice please

[Rekonn]

My 90g has been up and running for about 10 months now, and I think that 15g water changes with ReefCrystals twice a month aren't able to keep up with calcium demands anymore. Elos CA test kit shows 330ppm, and Elos Alk shows 5.5dkh. I'm going to eventually set up a drip, as shown here, but first I need to find out how much my tank uses. What's a good starting point?

I had a 700ml water bottle handy, so I used 1/4 teaspoon of kalk. I then made 6 marks on the bottle. This way, I add ~100ml per day of the solution (every couple hours when I'm home I add some till I reach the next mark). Does this sound reasonable? Or is that amount way too small to make any difference in CA and Alk readings?

 

[sfsuphysics]

If you have an stony tank that's fairly well established, I would be very hesitant to believe that kalkwasser alone can keep up with demand, not to mention kalkwasser will make your alkalinity creep up faster than your calcium, however there is some debate to how true this is.

As to figure out how much you need, you're correct in trying to figure out the demand, then use one of the many great reef chemistry calculators to figure out how much you should dose. What I would do is measure alkalinity as it apparently is readable a lot quicker, see how much it changes after a week or so without adding anything to the tank. Then use that to figure out your daily consumption.

One of my faves for calculators however all are flawed for telling you how much alkalinity you should have to match up with the calcium.
http://reef.diesyst.com/chemcalc/chem_calc3.html

 

[sfsuphysics]

Also, in order to get your calcium up from 330 to 350 with kalk, you'd need 2.21 gallons of saturated limewater. Which would be about 4.5 teaspoons of kalk...

 

[tuberider]

Check your reef crystals...

Also for an adjusment that large, I'd go with two part instead of kalk, and use kalk for top off once you've gotten the levels you like.

 

[Rekonn]

Thanks for the info! Do I need to worry about PH when dosing kalk with a drip, or will it only get too high if too much is added at once?

Any recommendations for the two part? I'm going to order more salt from DFS soon, so I can tack that on. Next water change I'll test the ReefCrystals too.

My tank has 14 small SPS or LPS frags and corraline on the back and bottom. Below is a month old pic and my tank journal is here.