A weekly treat for your fish - one half inch round slice of cucumber suspended on a piece of string, or attached to one of the tank's ornament/displays works wonders. They get a bit of stimulation and you can watch all the different species ways of dealing with and eating it.
We have a 5" loach which we have had for 17 years and the cucumber transforms a boring old sucker into an entertainer, he has been known to wear the cucumber as a collar.
I want to encourage youngsters (male or female) to get into the kitchen and enjoy cooking. TASTE it!