Discard-a-Stones are disposable air diffusers with reusable inserts for attaching airline. They are an excellent aeration device for use on undergravel filters,corner filters or just as decorations. Choose fine or coarse bubbles.
Would work very well if added to the inside of a Hydro Sponge Filter. This helps the sponge filter deliver a bubble stream.
I purchased both the coarse and the fine stones. They are slim enough to fit into air powered filters. They provide a more powerful current than traditional stones because they don't impede the air flow as much. I highly recommend them for use in filters.