I just got a bag of pool filter sand that im gonna use for my P tank and my feeder tank. Is it safe? I heard that it has something called silicates in it ? Is that harmfull? Caus Mine just says filter sand for pools on the bag. It looks more like real tiny white gravel than real sand. The grains look like small white crystals. the 22Kg bag cost me 8$ cdn. So is it ok to use ? Thanks