Vivarium fish

i am planning to upgrade my 18x10" firebelly toad tank to a 30x12x15" (or 30x18 if I can find one). As a water portion, I will be using a 12x8x8" tank or a 16x8x8, with land built up around it. Along with my 3 firebellies I plan to keep a couple of small treefrogs and possibly a day gecko and a small land dwelling frog. Are there any fish that would do alright in the small water area? It won't be heated but the room is warm (24C or so) in the day, 20-22C at night. If I can find a day gecko then I will add a basking lamp which will keep the temperature slightly higher. I was thinking endlers or something similar? the water area will be planted with low-light plants.

thanks,
momar

Thanks for the suggestions. Think I might go for white clouds...paradise fish seem hard to find in the uk