My advise would be to dose the calcium and then after 2 hours recheck all paremeters and see how the calcium dose has affected first the ca (rise) and then the ALK if this has been affected. If all stable do the same with the ALK, and keep adjusting both bringing them both up to adequate level.
Keep check on how much you dose of each to get up to the required levels then set the 1 x dose amount as your daily dose, and then after 48 hours re check. If one is dropping off or going to high you cna adjust. Of course you need to adjust the MG in the same way but you will find this the least dosed of all the elements. The ALK by nature will be the most dosed.
Do not fall into the trap of trying to get your Ca into the 400's it is not required, a healthy figure of 380+ and an ALK of 7 (yes 7) is ideal.
You will also get more help on this subject on the Fauna Marin forum on RC, drop by there and ask some questions to Fauna Marin directly