When the rocks looked right, I made a mixture of concrete and colored it with concrete dye. The charcoal worked well and I painted 3 layers of quikcrete onto the waterfall and rock walls. After they all dried, I used acrylic paint to add highlights and tint the rocks the exact color I wanted. I had never used the concrete method before and it worked well. The rocks were very real looking.
Then I built an egg crate stand that would keep the waterfall and planted area above the waterline. The waterfall rested nicely on this stand and then I spray foamed the two pieces together in the tank. I carved the foam once again and then put concrete on to lock the two pieces together forever.
I covered the egg crate with window screen below the waterline and then spread a layer of silicone onto the screen. It took some tender loving care, but I was able to press rocks into the silicone and it held really quite nicely.
Last edited by Learner; 11-23-2013 at 07:17 PM.