GATF are very stubborn to break into non live food. If you have other fish already eating then it won't be long before he gets the idea. They can go for weeks without food. It took my GATF almost 2 weeks before he caved in. Tilapia is only filets and I doubt have all the trace minerals. I still think pellets are the best so you could stuff some pellets into the anchovies. I would throw in some softened pellets when you feed and see if they hit it.
Anyway enjoy the video, play it in 1080p lol i used my iphone 4s so the quality horrible on anything under 1080