Hydro sponges are superb. You can run them straight, you can put a piece of short air tubing inside the actual sponge to get smaller bubbles, or you can put a standard air stone to get even smaller bubbles. They also sell their own diffusers that are, you guessed it, smaller bubbles still. It is an excellent quality sponge and the lift tube comes very long so you can cut them to size. They are also stackable!