Hi you can try several tricks
1 - place a mirror in a base of a plastic container - theory - fish see's reflection attacks it and presto fish is in container
2 - use two nets. A small 'chasing' net and a big one to catch the fish.
3 - place a fish bag in there favourite hiding place then when they retreat simply lift out the bag!
4 - leave the net in the tank for a little while,then they will not associate it with danger?
None of these are completely 'fool proof' so to speak so hopefully some one may have a simpler solution?