Having worked at one time for a saltwater shop, I'll pass along what I learned there. Use 2 nets. Or 1 net and your hand. Think like the fish, choose the path that they will take, and place one of the nets there and do not move it. Use your hand or the other net to drive the fish out of hiding and into the waiting motionless net. Takes a little practice, different species behave differently when being netted, you'll soon catch on.
Just please don't chase the fish around the tank with a net. It only creates stress for the both of you.