Originally Posted by TheCrazyFishLady
You want something porous. So, legos wouldn't be ideal because of their smooth texture.
Agreed. Legos are an interesting idea, but something like Fluval's Biomax has a much
greater surface area due to all the pores in the material. In addition, Biomax are extruded tubes, which lets water pass through & around, and solid Legos would not allow for this.