Calcium Test Kit Woes.

I am unable to get a reading with either a Red Sea calcium test kit or a Tropic
Marin. The samples simply -will not- change color. In the case of the red sea
test, the sample simply gets darker and darker pink rather than changing to
orange as it should. In the case of the tropic marin, the sample should go
from light blue to clear and it won't. Anyone have any ideas why? This is a
90g with moderate pre-established coraline growth and only 1 hard coral (lg
bubble) and six sinularia. The substrate is a 1 inch thick layer of Southdown
sand and I have a plenum with a 5 inch layer of aragonite gravel and some
crushed coral. The tank has been up since memorial day and I have not been
able to get a read on it in six or more tries. I also dose with Kent
Turbocalcium at a rate of 1/8 tsp 3 times a week. I have some new coraline
growth but it is small and slow. At this point I suspect that the Southdown
sand is somehow throwing the test kits off. It is the only thing that is
different about this tank compared to previous reefs I've run. Also KH is 9
and Ph is 8.2. TIA -M333