<p> A Pre Filter Sponge is the perfect tool to keep shrimp, small fish, and babies safe from being sucked up into the filter. The sponge should be placed over the intake tube, making sure that the fit is snug and secure. Acting as a mechanical filter, the sponge will trap larger particles, while allowing water and smaller particles to pass into the filter. Regular cleaning of the Pre Filter Sponge is recommended to prevent any blockage of water flow. Use tank water when cleaning the Pre Filter Sponge to avoid killing beneficial bacterial that may have colonized the sponge. </p> <table width="100%"> <tbody> <tr> <td style="width: 18%; text-align: center;"> Size</td> <td style="width: 18%; text-align: center;">Sponge Diameter</td> <td style="width: 18.1847%; text-align: center;">Intake Hole</td> <td style="width: 35.8153%; text-align: center;">Length </td> </tr> <tr> <td style="width: 18%; text-align: center;">Small</td> <td style="width: 18%; text-align: center;">1.5 inches</td> <td style="width: 18.1847%; text-align: center;">0.5 inches</td> <td style="width: 35.8153%; text-align: center;">2.75 inches</td> </tr> <tr> <td style="width: 18%; text-align: center;">Medium</td> <td style="width: 18%; text-align: center;">2.5 inches</td> <td style="width: 18.1847%; text-align: center;">0.5 inches</td> <td style="width: 35.8153%; text-align: center;">3 inches</td> </tr> <tr> <td style="width: 18%; text-align: center;">Large</td> <td style="width: 18%; text-align: center;">3.5 inches</td> <td style="width: 18.1847%; text-align: center;">1.25 inches</td> <td style="width: 35.8153%; text-align: center;">5.5 inches</td> </tr> </tbody> </table>