Is background safe?

Made concrete background, left it outside for about two months, then attached it to my 125. After attaching the bg I did some touch up work with cement. let it cure for about 10 days while doing water changes. After I checked my parameters and everything was fine for about the last three days. Would it be safe to go ahead and put fish in it? I already have some peacock babies in there and they have been doing fine for about three days? Do you people think I could go ahead and put my show tank together, or should I wait some more? PH is 7.8 and stable and the fish are doing fine.
Please let me know what you guys think I am really nervous about putting my show fish in the tank! I'd really appreciate some advice from experienced people.