It really does matter. Sorry Josh. If your aim is to ensure maximum oxygenation of the tank water, you want the return to disturb the surface of the water and prevent the water in the tank becoming stratified. If you have a light fish load and are using supplemental CO2 for plants, you want to avoid that good gas exchange by returning the water where it will not disturb the water surface as much. That way the CO2 you add will not be removed by that same gas exchange at the surface. I personally run all of my tanks for fish and treat my plants as just guests in the tank. The water in my tanks is constantly mixed to avoid stratification and I accept the fact that some of the CO2 I supply will be lost because of that good mixing.
A forum community dedicated to Aquarium owners and enthusiasts. Come join the discussion about collections, displays, product reviews, accessories, classifieds, breeding, health, behavior, housing, care, and more!