mounting shelf rock to glass

[toytech]

Is the tank dry or wet ? if its dry cut the rock with a tile saw to get a flat edge and silicone the crap out of it ( in a corner fith 2 sides of contact would be best) or drill pockets in the back and silicone some rare earth magnets into it , they all usualy have a weight rating to them but make sure to uprate your mags because there will be alot of leverage on them from a shelf piece.