The whiptails are very laid-back fish - they seem to be eating OK and they move around from time to time, but they're not very active. Sometimes I even see a snail crawl over the top of them, though they often twitch and try to throw it off.
Within an hour of putting the Otos in the tank I noticed an Oto on top of one of the whiptails. It stayed there for about 15 minutes, as shown in the photo attached.
This looks really cute, like it's having a piggyback. But should I be worried? Is the Oto eating the whiptail's slime coat? Is this a bad combination of fish to keep together?
Any advice very welcome - many thanks

Cheers,
Paul