Unusable calcium
 

Is there such thing as bound or unusable calcium? I probably don’t mean calcium bound with argonite or in skeletons or anything. More like in the water column.

Through trial and error, it seems my tank really likes very high calcium (like well over 500ppm). Things just seem to grow better. So this got me thinking, either my test kits are reading higher than the Ca actually is, or the test kits are also reading some sort of Ca in the water column that is unusable by corals, coralline, etc.

Thoughts?

Well what test kit are you using and have you tried a different test kit yet? Are you dosing? I can't imagine you having high calcium if you're not dosing...and you dont have a lot of calcium demands in your tank already.

High calcium levels can lead to fast deposits building up on your equipment. IE your pumps and skimmer intake...which means more cleaning of the mechanicals will be required.

I'm not aware of any benefits of having too high of a calcium level...I'll let someone else chime in on that.

Calcium inside organisms or bound into organics won't be available, but they also won't show up on test kits. I don't know of anything that would confuse a calcium kit. Maybe you're seeing a coincidence, a testing issue, or perhaps some parameter like alkalinity is a bit low. A higher calcium level should make coral growth a bit easier, but I would have guessed that 500 ppm is going to be close to the upper limit if other parameters are fine. I'm not sure, though.

@reefpuck: thanks, but I’m not worried that my Ca is high or the effects of it being high. I definitely made it that high myself. My question is more directed at the chemistry of... “free calcium”...

@beetoni: yeah, I am leaning toward not trusting my test kit. Will probably have a LFS verify. But I was also considering any other possibilities. And by more than 500ppm, I mean it tests at 800ppm. There is no “snow” there could be some crusting of my sand, but that’s about it. I know that sounds high, but my corals much prefer it. If I leave my tank at what tests at 400-450ppm, corals just kind of survive (no growth) and Coralline recedes. As a side note my alk tests at 8dKH and my ph is 8.2

800 ppm is high enough that I'm skeptical about something. :) I'm not sure what yet. I'd get second opinions on the calcium and alkalinity kits. 800 ppm is far higher than the calcium would need to be for good growth in reasonably normal water conditions.

My thoughts too. Either the tests (or person doing the test 0.0) or, I was wondering, some sort of unusable Ca being caught on the test. Thanks for your input!

You're welcome! Good luck!