I have a 55 Gallon Fresh water Tank with ciclids and Im thinking about converting the Tank into a Salt Water Predator Tank.I like the rocks I have in the Tank they are a mix of black and White pebbles.At my fish shop I was told that I would need sand,that pebbles would mess with the PH level.Im not sure if that is trying to make a sale or not,I would like your advice on this.Should I leave the pebbles or buy sand and put it in there.I want to leave them and drain the water and add salt water,I know this will kill the ecosystem in the Fresh water tank.I was told to bleach the old base rock,Im not to sure about that.The ciclids will go into a 40 Gallon New Tank I have.How would you convert to salt water without causing to much Damage.Tank will have a grouper and a snapper thanx for advice.