Went out to get another breeding trap and saw this 
It looks really funky and ingenius!
The mother fish is in the right hand section and there is a tapered bit in the middle and the fry fall through it and get into the bottom section...
there is an airline connected to the left hand box which draws water into it via the tube and the fry get sucked through the pipe between them!
Edit: oh and the left section can be removed without loosing any water so you can move the fry...
Cost £6.99
It looks really funky and ingenius!

The mother fish is in the right hand section and there is a tapered bit in the middle and the fry fall through it and get into the bottom section...
there is an airline connected to the left hand box which draws water into it via the tube and the fry get sucked through the pipe between them!
Edit: oh and the left section can be removed without loosing any water so you can move the fry...
Cost £6.99