INTRODUCTION: In order to make systems away from our first home, Earth, we need to think about a different kind of ecology, one that we will have to construct if a colony or ship is to be at least partially self sustaining.

• An introduction to closed cycle ecology.
• A Closed Cycle Prawn Experiment (in development) (more tank experients to go here eventually---i have done LOTS of them....)

All about Budgets: Humans (and animals) breathe oxygen, consume water, consume proteins and carbohydrates, and many trace minerals and vitamins. We exhale Carbon Dioxide (CO2), excrete water and salts (and other things). It will always be a bit expensive to ship the inputs up the gravity well to people in colonies or space stations, so astronauts must also be farmers. Plants and algae can convert our wastes and CO2 using light of certain wavelengths and water into food and oxygen. Animals can also convert plants and algae (and in some cases wastes) into protiens. Ships and stations have the tightest budgets...no more inputs other than light (others are very limited at best). Colonies and bases on planets, moons, and other bodies have some inputs, but they might need some kind of transformation. In any case, effecient farming (even on Earth) focuses on reuse, closing the cycle as much as possible. A thing to note about making an ecosystem, it takes lots of work to keep it balanced in a way we want. Near the sun we have ample sunlight (though maybe too much radiation..another topic), and likely ample energy (from solar, nuclear, etc.), so we assume we get these at need. We will then need to balance what humans need to take in. To do this mathematicaly we will need to find out how much each person takes in and lets out, and the same for any candidate species, including energy requirements (like heat, sunlight) and water. Ideally a profile of every species in the mix should be taken. For now lets try w/o the math. Lets assume we have a rotating space station (which provides some type of gravity) So what species should we consider for an example:

• Plants: Tomatoes are a very good start...they can grow in little or no soil, need less water then some other plants. Prickley Pairs might also fit into this model. Maybe some kind of legume if we have a very large area. From either we get oxygen and food. We (humans) provide to either waste (including waste water such as from urine) and CO2. Water will have to come from condensors (taking it from the air) and the toilet if it is a system of just us and tomatoes. Energy would ideally balance out the losses in each cycle from Tomato to Person to Tomato... Unfortunately, man cannot live on tomatoes alone (and who would want to?) so at a minimum other plants will be needed. As a start, some water beyond what people bring in there bodies will be needed as well, though an efficient system will minimize the starter water and any later water inputs (due to metabolic water loss...i.e. it takes water molocule to digest tomatoes and that water gets turned into cellular fuel..some is lost) Ideally, you would need a suite of compatible plants, such as soyabeans, and maybe simple organisms algae. The count would depend on how much variety you want in your diet and what greenery you want to see around the station (no reason one couldn't put mini tomato gardens everywhere there are people).

• Personally, I like eating fish, shrimp, and other things too, and I think it also good to see them, and they can act as a buffer for plants. In this case we need tanks. Candidate species include bighead and silver carp (very good at filering wastes and can be raised very densely), prawns (also a good filter), and tilapia (can be seriously crowded, just like the carp). One could then do a tilapia-tomato system (very common in home aquaculture fyi...), or a carp-shrimp-tilapia mixed arrangement, waste going through the plants/algae, then to the fishes. Dead leaves and plant wastes are great foods for the fishes mentioned too. Tight management of the water is very important (water is recycled then on many levels), so closed tanks, or tanks in areas with hermetic seals to prevent water loss (like a garden area for the crew to enjoy plants and fishes). If space is really limited, brine shrimp and krill could be used as well.