Caution: No lid or grate on top to stop fish from jumping in or pleco's getting in. There is enough room for fish that may jump and pleco's to get behind or around and trapped behind the media even though it has a plastic frame. A piece of plastic canvas over the top is highly recomended to prevent accidents here as pleco's get hung up in the media bag material. You could also add a small bag of bio media to fill in the large gap in the back or a sponge.