What would make Calcium go from 440 to 380 in 24 hours? 
Last night I tested the tank before I fed a new batch of phyto and the parm were
Alk: 3.0
Ca: 440
Nitrate: 0
Nitrite: 0
Am:0
Phos: 0
PH 8.2
Dkh 9.0
Salinity 1.024
The tank is mostly a softies tank and just added a sps frag (about 2 inches in size) sunday. Started running Carbon this evening after testing to protect the sps.
This evening before I started the carbon was as follows:
Alk: 3.0
Ca: 380
Nitrate: 0
Nitrite: 0
Am:0
Phos: 0
PH 8.2
Dkh 7.0
Salinity 1.024

Last night I tested the tank before I fed a new batch of phyto and the parm were
Alk: 3.0
Ca: 440
Nitrate: 0
Nitrite: 0
Am:0
Phos: 0
PH 8.2
Dkh 9.0
Salinity 1.024
The tank is mostly a softies tank and just added a sps frag (about 2 inches in size) sunday. Started running Carbon this evening after testing to protect the sps.
This evening before I started the carbon was as follows:
Alk: 3.0
Ca: 380
Nitrate: 0
Nitrite: 0
Am:0
Phos: 0
PH 8.2
Dkh 7.0
Salinity 1.024