Can I do this?

OK so I have a 55 gallon cichlid (no this is NOT a cichlid question) tank, and for that tank I have a 10 gallon quarantine tank. The 10 gal came from my mom who held a spawn from her pond, so the tank came complete with a few pond snails, one of which is still in there despite the tank sitting with 2 inches of water in it for weeks. Other than that snail and few little ones I added today, nothing is in the tank and well... its borning. I rarely use it as a hospital tank, maybe once every 2-3 months, but I am unable to tear it down and store it... so it remains set up in the living room, in plain view. So I would like to have 1 fish type inhabitant in this tank, just so people will stop asking "is there anything alive in there?" and because my kidss REALLY want something in there.
Is there anything I can put in there that can remain through treatments should one of my cichlids get ill, that will not cause undue stress to a sick fish ect. I think this will also help keep the tank cycled.
Now let me be clear... I could care less if I put a .15 cent feeder goldfish in there if it would work, but I am unwilling to pay more than 10.00 for whatver goes in.

Things I won't put in...
Aquarium crabs.. they never stay in the tank
ghost shrimp... die too fast
danios... ugly and too freaking fast to catch when i need to

aquarium frogs I like, but I am pretty sure any of my fish, even when ill would probably kill them

Any ideas?
No plants... not only do I kill them, but my fish ENJOY shredding them. I don't do real plants.

See thats what a wondered about. What about a betta and then keep a bowl on hand for him to reside in while the hospital tank is actually being used as a hospital tank? Then I could return him to the 10 gallon once its not in use and has had its water change. Think that might work?

Oh I don't mean one of those little 1 cup bowls, thats inhumane IMO

I mean probably a small 1 gallon for temporary use, I will supply it with air, but not sure on filtration. For heat I don't know what I will do, do they sell heaters that small? If I don't have filtration it would have daily water changes and ofcourse the water would be dechlorinated. I need to make it as low key as possible, otherwise hubby may freak out if I make a whole new setup!

I was thinking about doing THIS though it would involve keeping a plant alive... not so sure about that

Somthing like THIS is intended for temporary housing, which is all I need, 10 days worth of housing for every 3 months or so.

Or THIS

And I love THIS but that would look fuinny hanging on the wall without a full-time resident, lol. Maybe a plant? Here we are at the plant thing again... I DO have a live bamboo plant though if hubby had not rescued it recently I would have killed it too.

Think anything like this would serve well as a TEMPORARY housing? For only those times I am using the isolation take as an isolation/treatment tank?

OK, I still think I want the wall unit for my bathroom bamboo plant though, will look better than the vase its in, lol. Maybe a fake fish for that one...

Can anyone tell me how to choose the best specimin, its coming from the LFS with a small selection, nothing special, just a fish to make my kids happy. Is there anything I should look for or look to avoid? The last betta I got (for my mom, to replace her's that died) only lasted a month in one of those plant/vase setups. The one she had before was also in the plant/vase setup and did very well, he was a happy, social fish. He lasted a LONG time I think too.