Yes and no . Expecialy with the snorkel and aquablocks. That void will act as a cave for all kinds of criters microbes and such to live in the settling chamber of those blocks will alow it to fall to the floor and decay. Which is food for those living there. I even found koi in there the first year . My snorkel and centepede are 24 inch culvert with aquablocks above a layer of mellon sized rocks to the sides and then 18 inches of gravel above the blocks.