awesome thinking. i was wanting to silicone some lava rock to the back of a 5.5 for moss.. but if i can just spackle some concrete on the back.. hmmm..
flashbacks to pouring concrete with the step-dad... foam thingy.. what is the foam thingy.. expansion joint.. note to self: do not blindly pour concrete ready mix into empty tank...
i think your idea will work well long term. just keep doing your regular w/c schedule so the concrete doesn't put off too many minerals. a 3d black concrete wall would be sick with some moss and ferns on it.. you could even fashion little cup like indents in, fill them with some high CEC soil and plant stuff on the wall.
edit: your post still pertains to the scape of the tank, regardless of how awesome it is to do things like this by yourself. don't sweat it.
Last edited by steven p; 10-18-2012 at 08:03 AM.