The original filter was completely submersed. For this  filter, i want to  only have the pump submersed, with a prefilter to avoid sucking small fishes and shrimplets into the filter. The filtering masses will be in a box over the water surface, in order to have it easily servicable. The plan is to have a rectangular box, with one water input, and one water output, and multiple compartments. The closer from the input, the larger are the holes in the filtering mass. I thus will place large holes sponge near the entrance, smaller holes sponge afterwards, then perlon in the third compartement. I will leave the last compartment for biological filtration mass.

However, i may later use a specific design for biological filtration, with cascading water flow, as it maximizes the oxygen entry into the water and thus bacteria developpement (it is call semi-submerged filter). For now, i want to have a good mechanical filtration, and have it easily servicable.