Awww bless - sounds so cute!
The only strange fish relationship I've had in my tanks was between my extra large female guppy and a rainbow shark. They were the only two fish in a 2ft tank for quite a few weeks (I had to do a fish-in cycle which wasn't intended but ended up that way on that tank due to necessity of rescuing the female from a bunch of harrassing-to-the-point-of-death males - and the rainbow shark was being a very bad boy, constantly attacking everything that moved).
Anyway, in went the guppy first, all on her lonesome, then the rainbow shark a couple of weeks later. They followed each other around the tank like best buddies LOL - even when they were resting they'd be close to each other. Really, weird!!
But once the tank was fully cycled and I slowly added new fish, the rainbow started up his old bullying tricks again - so I had to move him to yet another tank. He's now in a 3ft tank with just two pink convicts - and no they are not friends but he stays mostly one end of the tank and the convicts, well, they own the whole bloomin' tank as far as they're concerned! Rainbow is just their lodger and wouldn't dare mess with the convicts LOL
Felt a bit guilty for splitting up the Rainbow and Guppy friendship, though
Athena