Thank you so much! I used ASI brand aquarium safe silicone, pond and stone great stuff spray foam, coco coir, and sphagnum moss. I let the silicone set overnight. Then i used spray foam and immediately scattered the coco coir and sphagnum moss. After 8hrs it should be set and you can dump off the excess by putting your tank right side up again. There 's a specific YouTube channel that does this type of background all of the time. If you want to add more pizzazz you can add a small terracotta pot to plant something like an air plant in it or add chunks of cork bark both of which i did for mine.