I'd stick with Zoo Med for calcium and multivitamin powders , these seem to be very good quality.
I've only used Zoo Med and AristoPet.
I wont use AristoPet Calcium now as they changed their process and the powder is now courser and contains very sharp bits of oyster shed (and I also found some steel splinters in the last few bottle of it I bought , I then swapped over to Zoo Med's products).