Marina 5-gallon aquarium filter house

This is a custom filter house I designed for the Marina 5-gallon aquarium kit.

The stock setup uses a hang-on-the-back filter, which isn’t great aesthetically. On top of that, replacing disposable filter cartridges every month disrupts the nitrogen cycle and gets expensive. The heater is also very visible, which I wanted to avoid.

This design solves those issues.

The filter house uses the original Marina pump included in the kit. As shown in the diagram, water is drawn in from the bottom, then the pump pushes it into a separate chamber. Thanks to the internal baffle layout, the water rises from the bottom of the heater to the top, warming evenly as it passes through. After that, the water flows through the filter media and exits through a wide discharge outlet.
Because the outlet spreads the flow across a broad surface, the surface agitation stays gentle—perfect for bettas or other fish that dislike strong currents.

From top to bottom, you can load the filter house with coarse sponge → fine sponge → ceramic media.

This setup works best when the aquarium is placed in a tall, vertical orientation. I tried printing the filter house in several colors, but black looks the best in the tank.

Feel free to download and use it. If you find anything that can be improved, let me know—and if you print and install it, I’d love to see photos in the comments.

Tip: To prevent the filter house from floating, fill it with water first before filling the aquarium.