Algae tanks are often considered for use when designing the air recycling of Lunar bases, Mars colonies, and rotating space stations. Such are most common in highly centralized air and food production system designs. Such are unforgiving of mistakes, easily contaminated and create additional failure points. Decentralizing such systems isn’t an option either; bubbling algae tanks in every room are too fragile. They require precise PH, temperature, nutrient, and mineral control. Contamination can quickly wreck them. Even unfiltered air can upset them. An alternative to having an algae tank bubbling in every room is to have well-planted aquariums in each room of the living sections.
What small efficiency is lost in the decentralization of big bubbling vats of algae into a room by room of planted aquariums is more than made up in durability and robustness of the system. The aquatic plants available come close to being as effective as algae while at the same time being evolved to tolerate a far wider range of conditions and be better suited to surviving contamination. A properly set up large planted aquarium can process all the CO2 a couple of people produce. If one becomes less efficient it has little effect on the others.
Unlike Algae tanks, such a setup is also effective at air filtration. Aquariums make these rooms fresher, and more alive creating a far healthier environment for the people living there. Both must be harvested almost daily. Algae produces algae proteins, sugars, and enzymes. The plant, insects and small fish harvested from aquariums produce those and a wide range of other proteins, sugars, enzymes, and fats that the enclosed biosphere needs.
Then there is the psychological benefit of having numerous aquariums. Many studies have demonstrated how having aquariums in rooms increase mental stability. The effect can be seen in rural environments and is far more pronounced in urban homes and offices. Away from Earth, with no easy access to outside, this helpful stabilizing effect should not be left out.
Algae only works in centralized systems, and is problematic there. Centralized systems may work for ships where mass and volume constraints are ultra-critical concerns. On colonies, bases, and stations decentralized room by room systems are better for many different reasons. It is more robust. So robust in fact that it is close to impossible to damage a significant amount of it at once. Another important factor is; if each apartment, office, hall, business, and home is taking care of its own air recycling, then no company or government gets to say you must pay us if you want to continue to have fresh air.
Any of these reasons are sufficient to favor decentralized planted aquariums optimized for O2 production, over large central algae vats. Done correctly this system will require supplement CO2 from other sources than just the people breathing in those rooms to maintain peek performance unless you routinely overcrowd them or have too few.
Aquariums everywhere many be the way the future Lunar base, Mars colony looks.
Eptle 