Game On!

So, I sit in this biology class with The Kid.
They have this project coming up that seemed pretty cool so I thought I'd take a stab at it.
What the students have to create is a biosphere.
The examples they were shown involve placing some living things in a one litre water bottle and sealing it up to see how long the things will survive.
Okay, this is not like ship in a bottle; they cut the water bottles in half, insert said living stuff and then tape the bottle back up.
Now, I know there are those biospheres out there with the glass globe and the shrimp or something, but this project includes something different.
They must build in a level that includes some soil so they can put in a plant.
It should look something like this:



Oh, and this is not a terrarium.
The vehicle should be sealed airtight.
Anyways, it's an interesting project.
Me likes interesting projects so I thought I'd give this one a shot.
Some things I've thought of:
Plants: What kind of plants can live in water and essentially scrub off the CO2? I'll also check out some hydoponic plants.
Animals: Okay, I confess. I know where to get the shrimp that lives in that commercial biosphere. I was actually thinking of brine shrimp or something but we'll see what I decide.
Water: Big question. The commercial version uses some sort of additive(nutrients, etc.) to the their water. More research needs to be done here.
Volume: Biggest freakin thing I can find! Not really. I think a large volume will help though. Start off with as much O2 as possible.
Vehicle: Biggest freakin thing I can find! Maybe. I was sort of thinking those five gallon water cooler thingies. Not sure about the UV protection though as I assume the environment would need UV light.
Now since this is a home thing for my amusement only, I think I'll leave myself open to the design and the requirements. I'm not sure if I'll actually use soil, or just an aquatic plant. Key here is to sustain the living animal/animals.
The excitement is building here as I start to put things together. This isn't the type of thing you put together overnight so I'll be giving it some thought.
Oh, and any suggestions would be welcome.
I wasn't a science major don't you know.
Anyways, I'll keep you posted.
Get it? Posted?
Nevermind.