Alk good, Ca low. Fix?

[Velodog2]

I've been dosing my little 18 with 2 part Cbalance since Nov 2013, slowly increasing dosage until I'm up to 7.5 ml/day now. Alk has risen nicely from 6.7 to 10.3 where I'd like it to stay. Ca however has remained at 375 this whole time. I'd like it to be around 450 I think because although I'm finally getting a little coralline growth it is very slow. I'm using good Red Sea test kits. Oh, Mg ranges from 1240 to 1560. That test seems a little spurious but the level doesn't appear to be low. I also do a 5 gal water change each and every week with plain old instant ocean and ro/di water that reads zero on the TDS meter.

I have a passive kalk reactor that is just running my top off water through a kalk bed that is stirred manually only once a week. It may not do anything significant.

The tank is mostly sps and those are mostly acro. There is a 3.5" crocea clam as well however.

Other than lack of coralline good things are happening with generally good coral growth and a nice steady progress in my battle first with cyano and then w hair algae. Both are well under control now. I run about 3/4 cup of GFO in a bag in the sump that gets changed out when I see algae growth pick up - about every month or two.

What would you do? Keep increasing Cbalance dosage? Do something to bring up just the calcium? My understanding of reef chemistry is not quite at a Randy Holmes-Farley level so schooling is fine here.

 

[mike007]

Yes you can raise your calcium by itself. I would recommend 425 as a good target. 375 is not that bad. How are you dosing and how often?

 

[Reefing Madness]

With your other elements in order, you'll be fine upping your dosing on Cal to get it to your liking, just like you did with your ALK. With what you have in your system, your using a bunch of Cal and Alk. You got some big calcium useres in there.

 

[Velodog2]

So how would you recommend raising just the calcium? 375 is ok true but certainly on the low side and I would like yo get better coralline growth. I'm currently dosing both parts at 7.5 ml once per day.

 

[mike007]

Use more of the calcium additive to bring level up to where you want It. Once you get both levels where you want them quit dosing for3 days and then retest and see what your consumption Is for your tank. Then divide by 3 and you will know your daily loss. Then you can go to the reef calculator and it will tell you how much to dose each day to maintain these levels.