DIY aquarium background - 90 gallon made from styrofoam and cement

This 90 gallon background was built using a horizontal stacking method. The styrofoam pieces on the bottom are intentionally flush with the sides and back of the aquarium to create a type of "shelf" that's higher than the substrate in front of the background. The idea is to help discourage substrate from accumulating behind the rock formations. Generous amounts of GE brand Silicone #1 were applied to all surfaces where styrofoam or cement met glass. Even with three coats of cement, these pieces would easily float if not secured in place by the silicone. Once the lower rock formation sections were built and siliconed in place, the rest of the background was built up from there by applying single pieces siliconed directly to the glass. With all the cement and and liquid acrylic work completed, the cement was allowed a few days to finish curing before beginning the tap water rinsing process. This was an exciting moment during the build process. After several weeks of work, the garden hose fills the tank for the very first time to begin the tap water rinse. The tank will soak for three days, be drained, and filled again. This process will be done three times for a total of nine days to help leach out excess calcium and magnesium from the cement.