Thoughts on the station's biosystem

Warning: this post was typed while getting ready for bed. Expect
spelling mistakes and things that were accidentally left out.

Well, goats seem to like climbing on things, which can be bad, and in
most respects probably aren't very different from sheep. Therefor I'd
suggest sheep over goats.

Chickens are basically feathered hogs, except that hogs probably won't
eat some things that a chicken will. Also, their manure tends to leech
nutrients from soil unless properly aged. I think it's a bad idea to
have chickens anywhere other than the agricultural rings.

Rabbits produce manure which is instantly usable, provide meat in an
efficient package, and some can provide fur for clothing.
Unfortunately their breeding is somewhat work-intensive.

As for releasing rabbits into your green section, I don't see a
problem with it if you use the following model:
Take a standard O'niell cylinder and make it larger than normal. Have
the mirrors constantly reflect light into the windows. Place another
level in the middle of the cylinder, somewhere closer to the normal
inner diameter of an O'Neill, and rotate it at a slighlt different rpm
than the outer level. This produces your day/night cycle. It's
preferable that the inner layer be composed of solid sections and the
supports only. In the lower level you start growing a lot of biomass
on the land portions, while on the upper level you stick the
residential sections. Once you judge the level of biomass on the lower
level high enough, you release rabbits down there, along with ferrets,
coyotes, hawks, snakes, and other predators. This gives you a
functional ecosystem down there, and the rabbits will probably grow
plentiful enough to be reasonably easy to harvest as a little protien.

I'd personally take this system and use the windows as lakes/plankton
farms. You just need to make sure you have enough bottom feeder fish
to keep the windows clean. Then you feed the lake water into krill and
shellfish tanks, then into fish tanks along with some shellfish and
krill meat, and then back onto the lower green level as fertilizer. I
just wouldn't suggest using it to make rain.

If you want more oxygen then you cover the bottom of the inner level
with clear open topped jars, fill them with plankton and water, and
stick an aerator in them.