Can you overdose on Ca?

[thriceanangel]

Is there such thing as having too much calcium in your tank, or is it only too much if it precipitates out.

[bertoni]

Too much calcium in the water also can lead to a lot of abiotic precipitation, which can clog pumps and coat heaters, for example. That's also a waste of the calcium supplement. Other than that, for at least short periods, high calcium shouldn't be a problem. I don't know of any studies of long-term effects, but I wouldn't dose calcium above 450 ppm, personally.