My flier Bob learnt this trick to attract my attention, it started with just swimming nose down backwards, which of course I would go upto the tank thinking he was ill, then he added the flip lol. He was in a tank on his own after a disagreement with the Urau. The tank is my quarantine tank in the kitchen so it gets a lot of traffic and while Bob was recovering he taught himself this......
http/www.youtube.com/watch?v=Wy_01IBEtHY
When I moved him to another tank with angel fish he has not done it since.