The primary goal of our inflow/outflow design was to help improve circulation by the following:
Outflow: The outflow funnel was intentionally pointed slightly downwards. This improves water circulation to lower parts of the aquarium, where stagnation points often occur. The funnel, when completely submerged, creates less surface agitation to reduce CO2 loss to the atmosphere. At the same time, if turbulent surface aeration is desired, it can be done by raising the funnel halfway above the water line.
Inflow: CAL’s inflow contains narrow slits throughout the stem spanning from near the bottom end, to quite high up. The placement of the slits were intentionally designed to cover more vertical area than existing designs. To us, there really isn’t a good reason to place the slits just at the bottom. In fact, while they are much easier to manufacture, we found that having slit(s) just at the bottom strains the circulation, as water can only enter at the bottom. Since our outflow moves water across the depth of the tank, we needed an inflow that can take water in at various depth of the column, not just the bottom. Our flowfield tests also shows that they create a more uniform circulation pattern.
The slits on our inflow are also slightly wider and more in number. We want to make sure that enough water can pass through to the pump, and small blockages due to leaves or debris will not choke the pump.