Yup, they stay at the surface all day, but will go down to hunt. More than likely once you intoduced him into your tank you wouldnt see your loaches again. I kept khuli loaches with him at first but they always hid under a rock and wouldnt come out. I then put them in a different tank and put in zebra loaches. I didnt see them for over a month, I thought he ate them. One day when I was cleaning a piece of fake driftwood I found them jammed in a hole. I got them out and released them in the other tank with the khulis. Just the sight of the butterfly strikes fear in smaller fish.
If you do get one they can eat floating pellets and they love crickets. I would even feed mine spiders and moths (when the store was out of crickets.)
Theyre sweet fish, but they dont really do much...