Silica free would be just as good. Mine must have been cause I did a silicate test and it came back at 0. but silcates will only encourage some algae growth if I'm not mistaken, it wont have any detrimental effect on your fish.
In addition, someone posted an article here not too long ago about the benefits to having silicate in your system. It's not all bad.
It is a pain to rinse it out though, I'll tell you that much. I had to rinse 250lbs of the stuff. LOL
180g Reef - 60g Rimless Reef -90G FOWLR- 125g Malawi Cichlids- 40b REEF- 34g Fresh Planted-working on- 20L FOWLR- working on
I have a mix of many different saltwater fish amongst my tanks, but I love my Tangs most of all.