getting a fast fish out

[evil Nick]

I have a flying fox that has been HARRASING my amazon puffer to no end. This started all of a sudden as well and usually only around feeding time. Outside that they can be right next to each other and usually act fine. Im waiting for my puffer to turn around and take a nip at it but he never does. Id rather keep the puffer and get rid of the fox to be honest even though I love foxes.
Problem is I can NOT catch him. Hes just to fast. I looked at making a fish trap but was wondering if there was a cheap and easy one like the inverted soda bottle top half thing that might work?
I dont even know what I would use as bait to lure it into anything.

 

[ZxC]

Large net propped against the glass / substrate, scare him/her into the net.

I had to do this with my denison barbs

 

[kashif314]

Large net.

 

[Brookster123]

Find out where he sleeps at night and go in under the cover of darkness. A red spectrum light can be used as the fish will not notice as much. You should probably play the mission impossible theme in earbuds as well. God speed!