PSU are you saying that they use Tropic Marine or Tropic Marine PRO?
I am curious too as I currently use reef crystals and wish to change to get more calcium.
A freind of mine used -- and had alk problems. It was 4.5 right out of the bag and clouding up his water. Also PH of tank was 7.9-8.0. Happened as soon as he got in a new batch of --. He switched to TM and his alk is now 3.5 and PH 8.1-8.2 after only 2-3 weeks. He is much happier. I am thinking of switching myself.
Tropic Marine has also been the most consistent from batch to batch, the magnesium levels are just about perfect. Yes, it's $$ but well worth the extra $20