I have done them with really strong magnets. You silicone the magnet into the styrofoam and then have the connecting magnet on the outside of the tank. This makes it so the aquascape can be removed if you wish at a later time. Placement of the magnets is critical, and it can take a lot of them, but this will hold it in place without having to silicon it to the tank.
MFK IS LIKE A FREAKIN DRUG AND COST HELLA MONEY TO








