I am starting to make the rock background/filter area for my fishtank/terrarium. Here is a picture of the corner rock that I made out of fiberglass. It is 16 inches high, but will be on more of a "ramp" also fiberglass to make it go to 20 inches.
This is the rough structure which I made of corrigated cardbord and duct tape. The blue horizontal line is about water level. The other blue line is the trickle of a water fall.
This next is a first layer of fiberglass. I decided to go to layers of fiberglass which you can see is kind of clear, and then I will sculpt and texture on the top using auto body filler, hopefully with pigment (I need to source some), and then seal that under some more resin.
here is the look with 2 layers of fiberglass, and the light on it from a different angle.