Chemistry Issues..

[SmallFry]

Hello Everyone..

I have something a little odd going on chemistry-wise.. I was trying to get to the bottom of why my two bubble tip anemones were spending a fair bit of the time deflated and wouldn't eat, so I did a full set of tests on the water, which I don't usually do (with about two coral frags, calcium is not really something I worry about a lot)..

Anyway, here's what I got:
pH 7.8
Alk 5dKH
Calcium ~880ppm!

I thought my test kits were off, so I tested a fresh batch of water (reef crystals) which seemed reasonable:

Alk 10dKH
Calcium 480ppm


Seems like the test kits aren't too far off. I'd noticed the alkalinity being low before, and raised it with baking soda, but it has obviously dropped again (a lot).
I don't have enough corals to be using any real quantity of calcium or alkalinity, but I have been noticing the venturi on the skimmer clogging a lot recently - I don't know if that's relevant or not.

I am wondering if there is something strange going on with my DIY rock, it seems to be breaking up a little. It has been in there about 18 months I think and was cured before it went in there. My thought is that the rock is leaching a huge amount of calcium which is then precipitating out and taking the alkalinity out with it. Before I go and replace all my rock, does this sound reasonable, likely or possible?

Thanks in advance..
Rob.