I'm not very good at planning things. As a result I've become very good at doing things two or three times to get it right.
For my background on my 40gal I decided to use quickcrete bonding adhesive mixed with coco fiber. It went on great and looked great when it dried. The only problem was when the background was wet the coco fiber would become very soft and flake off. For some people this might not be a big deal if your background is going to be covered in plants.
I decided to tear it down and start again. So for my next try I used the brown silicone method. So I spent 15 minutes inhaling fumes and spreading the silicone all over the foamed background. I then pressed dried coco fiber into the silicone. The next day I gently brushed off the excess coco fiber. To my amazement not a single strand of coco fiber stuck to the silicone.
In desperation I picked up a bottle of glue from my girlfriends office. She is a project controller for a company that reinforces aging cell phone towers. The glue they use is completely nontoxic even while it's drying, and when dry the glue is not brittle and will withstand extreme conditions. After spreading this onto the dry brown silicone I then pushed coco fiber into the glue and let it dry. This glue worked great the coco fibers didn't stick to the glue but all the dust in the coco fiber did. So the background doesn't look as soft and rolling as it did with the concrete adhesive method. The new background is pliable yet you can't scratch the coco fiber dust off. If I wanted to I could even stick toothpicks through it.
When the glue first dried it gave a white tint to the background as you can see in the pictures, but now the background is nice and dark.
Here is my tank after planting.
This is the tank one month later. I added some orchids from Andy's Orchids.
I'll post later with more pictures.