This sponge filter is designed to be snug in the corner for efficiency. You can oppose them for water flow, too. The lid is loose on purpose and is meant to either be glued on or bend the tabs with heat to make a snug fit. The bubble maker gets friction fit into the air downtube and glue the downtube to the lid. The airline adapter is also meant to be glued in place. All the glue is to prevent air leaking in crucial areas while maintaining printability and optimization for printing. For weight you can glue a rock to the base or use suction cups on top to prevent it from lifting. Silicone 1 is recommended or super glue gel, both are safe for fish.

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