Ok, so i had a 10 gallon that i was originally going to make a terrarium with... but changed my mind and decided to make another fish tank.
Steps i used to make the background:
1. covered back of tank w/ silicone, and let dry 24 hours.( so that foam sticks better)
2. covered that in great stuff expandable foam.
3. cut foam into shapes i wanted.
4. used some tile grout/ acrylic admix/ and acrylic craft paint... all mixed together, then painted onto foam.
5. use watered down acrylic paint to cover background again to give it a more natural rock look.
I also removed the rim off the top of the tank just because i saw others do this and think it looks cool.
I know that the mortar will bring the pH up, but as i was putting the mortar mix on i constantly sprayed it with vinegar to help to neutralize it... Now i have been filling it with water ovrnight, and doing 100% water changes everday. This is so that EVENTUALLY the mortar will finish curing and be neutral. I've been monitoring the pH everday and it's still increasing.... but a little less everyday.
Now, i did this technique in my 55 gallon paludarium, and it didn't take very long for the mortar to neutralize, but then again there is alot less exposed...
I'll post some pictures tonight so you guys/ gals can see the results.
(I think it looks awesome!
If there are any questions/ concerns, please let me know.