Butterfly fish would be cool, the current stock do seem to spend a bit too much time around the bottom. I'd need to save for a bit to get a few of them though.
Yea, I'm definitely hoping for some spawning from the heckelii fingers crossed for both sexes.
mcrudd, the tank is about 650 litres, 6' by 2' by 2'
Ismart I may take you up on that as the tank I've put them into has a lot of CO2 going into it so not sure how well they're going to be in it.
Thanks everyone else for the comments I just need to leave it alone now and let them grow!