I agree that toads are fairly active and might need more room than that, especially the big ones. I don't know about Asian toads in particular, but most toads really like to dig. Be prepared for them to kick dirt into the water!
Some people on the forum have mentioned there are studies that suggest frogs might need some UV light but it's still not entirely certain how much. I'd say a weak UV light couldn't hurt if you want, but definitely try supplements.