Bait a net. If you have a few days, it works rather consistently. Take a large fishnet, put food in the net, then just let it sit in the tank. Let it sit there, walk away, take it out after maybe thirty minutes. Only feed your fish way for the duration. Most fish get over their apprehension of the net within a few days, and then it's a simple matter to simply scoop out the fish while it's in the net getting a meal. I've been using this trick for decades, and it's worked on clowns, damsels, cardinals, triggers, angels and even shy feeders like marine bettas.