The cement was cured for almost 4 weeks before I started the rinsing process. The internet lead me astray. I don't know how people are successful with cement backgrounds. Everyone please be aware this killed my babies in 2 days! 4 year old toadied in 2 days!!!! Lesson learned my friends, lesson learned. I ripped the platform out of the tank and will be rebuilding with foam and pond paint again... Grrr.