Terrarium + Betta?

[dogmelissa]

Ok, I know the Betta topic has been covered in quite a lot of depth here, but I read through most of the posts related to them and I can't find what I want. I also did a fairly extensive internet search and can't find what I want. So here I am, back to my trusty pet lovers at pets.ca!!

I have a 10 gallon fish tank (was used as a dwarf hamster cage until the hammies died). I have been bitten by the gardening bug, and recently ran into the concept of terrariums in fish tanks (see Sample Ambhibian Terrariums or Kid's Terrarium). I don't have space in my house for anything as big as the first link and the second one rules out the possibility of having a fish in the tank. So, what I want to try to do (key word; try), is to somehow make a water-proof barrier across part of the tank, so that I can set up a terrarium on one side and put the Betta on the other. Failing a permanent barrier, I'd like to have a terrarium in a smaller jar or container that's in the tank, but not in the fish-water. (I can picture this in my head, I just don't know if the description is coming across). Something like an island or one in each corner of the tank or something.
Ok... have images in your mind of what I'm trying to accomplish? No? Ok, here's a link to something that's getting close, but obviously this water isn't self-contained: Terrarium with water In my mind it's just a simple acrylic divider (maybe in an arch or interesting shape) that's siliconed to the bottom and sides of the tank to the height I want. The stuff on one side for the plants won't leak over to the fish side, and the water in the fish side won't leak to the plant side.

Beyond the construction of the fish-tank partition, what I really need to know is how do I set up a Betta in a 10 gallon (or 5 once I have it divided) so that I don't have to turn the tank upside down and completely empty it to clean it? Can I set up a filtration system to keep the water clean? I know that bubbles in the water are bad for Bettas, so I'm not sure how to go about doing this. Obviously I will be changing the water, but I'm also not sure how to do that when I will have things in the tank that can't be moved. My thoughts are that the Betta would be probably in about 2 gallons of water (maybe a little less once it's all done) and would be the only fish in there.
Links, photos, etc would be much appreciated.

Thanks in advance,
Melissa