I'm trying to set up a very small tank for my girlfriend. I have a one gallon glass bowl and I want to make a somewhat ecological tank with plants, snails, and 2 fish. It will not have any filtration besides the plants and the only light source will be occasional trips to the window sill (if it's not too sunny). I will also change 10% of the water once a week. Besides, a betta, what would you recommend? I was thinking about some baby platies or baby guppies. Or would 2 adults be ok too? What other tough fish could I use?