just put a piece of paper, or some ther solid surface, between them and *poof* you'll have two fish going "Where he'd go?"
LOL my VT male does that with the mirror!!! haha
He gets all nasty at the mirror, even tries biting his own reflection, and as soon as I take the mirror away he darts around thinking 'Where the hell...o did he go!?'
One night I even found him stalking round where I put the mirror up against the tank, darting away and then back again.. lol Probably thinking 'I know he's still around somewhere!'

Theyre fun to watch, definitely!
Everytime I walk into the room he gets all excited, and when I look at him he does a lil butt wiggle and dance hahaha..
(Hes probably thinking im going to feed him though.. he's such a pig!

)