I have a seperate 35 gallon Hex, Seahorse tank. I'd like to create a tall pillar in the middle of the tank. I did so already, but the smaller rocks in the upper half of the pillar simply fall off. I was now planning to use plumbers putty to try and connect the rocks and stablize them. Do you think this will be strong enough? Were not talking large rocks here, the bottom most rock is roughly the size of two good size fists and progressively smaller to the top piece bieng half of fist or smaller.