Well, I've found the way to do a head count. Bloodworms! It was hilarious to watch. All 5 came rushing out and made a beeline for the food- and then had no idea what to do with it. They tumbled over the food and over each other like pigs in a trough. They obviously weren't fed such expensive delicacies in the lfs. It took them several minutes to work out what to do with it- but then they hoovered it up. I think we'll have a weekly treat and head count! And perhaps I could try some veggie matter in between.