I'm not exact on the dimensions, I think 48X18. We currently have about 9 shrimp (peppermint and camel) 1 CBS, 5 small light blue fish (not sure the same, they were the first inhabitants), about 20 snails, 2 pistol shrimp, 1 brittle star, 15 hermits, 2 emerald crabs, 1 mandarin, 1 shrimp goby...