Unavailable calcium?

[zachofalltrades]

So every time I test my tank for calcium it falls in the range of 380 or so. Now I don't have a reef tank, but I haven't seen any new coraline growth in the tank several months. I don't think my calcium is low enough to warrant no growth. I just replaced my bulbs as they were about a year old, maybe more. I have wellwater but no ro/di unit. I use the tap water filter that API puts out which is basically a carbon canister with a second stage of DI resin. I ordered a new one of those too since it's probably at the end of it's life, so is it possible that I'm getting a form of calcium from my tap water that's not getting pulled out by my aged filter, and it shows up on the test kit as being within normal limits even though marine life can't use it? I use instant ocean salt mix in case anybody needs to know.

 

[Randy Holmes-Farley]

No, I don't think the calcium is limiting coralline. No, there are not different forms of calcium to worry about, as long as the water is clear.

The things to check would be alkalinity and magnesium (you want normal to high on these) and phosphate (you want low but not too low on it). reduced organics also can seemingly help coralline.

These have more:

Reef Aquarium Water Parameters
http://www.reefkeeping.com/issues/2004-05/rhf/index.htm

The “How To” Guide to Reef Aquarium Chemistry for Beginners, Part 1: The Salt Water Itself
http://reefkeeping.com/issues/2007-03/rhf/index.php

The “How To” Guide to Reef Aquarium Chemistry for Beginners, Part 2: What Chemicals Must be Supplemented
http://reefkeeping.com/issues/2007-04/rhf/index.php

The "How To" Guide to Reef Aquarium Chemistry for Beginners, Part 3: pH
http://reefkeeping.com/issues/2007-05/rhf/index.php

The “How To” Guide to Reef Aquarium Chemistry for Beginners,
Part 4: What Chemicals May Detrimentally Accumulate
http://reefkeeping.com/issues/2007-09/rhf/index.php

 

[zachofalltrades]

Oh ok, thanks.

I've been testing my water since I made my post.

Nitrates 10

My alkalinity test kit is not precise at all, meant more for giving a range as low, normal, high. Normal on the kit being 1.7-2.8, my color seemed right in the middle of it.

Phosphates 0.0 (test goes on 0.25 ppm increments)

Oh and I do not have a Mg test kit yet.

 

[Randy Holmes-Farley]

You may need better kits to diagnose these issues.

phosphate at 0.02 ppm is OK. Phosphate at 0.15 ppm will likely deter calcifying organisms.

Assuming that alkalinity is in meq/L, you want to be above normal on that test, which is presumably for a fish only tank. 2.0 meq/L is tooo low. The links have more on target levels.