It is the easiest project. And kids these days never get to play with dead things so there was the inevitable fish fight.
All you need is a dead fish, fabric paint and a blank T-shirt. Though it turned out to be the most expensive of my eco class projects so far. The fabric paint is so pricey and the kids love squirting most of the bottle on. (In one of the pictures below the fish has about $5 worth of paint on it - deep breath)
I usually get a few small frozen tilapia because they are only a couple dollars each. But there seemed to be a shortage. I went to several stores and struck out. So I bought a milk fish (that unfortunately had already had it's scales removed) and some salmon heads. My last stop, at an Asian grocery that I had never been to before, had bags of small frozen river fish.
The fish heads were the most interesting (and the kids had the most fun with them also - putting "make-up" on them and such) One ended up looking like a nuclear hazard sign and another like a butterfly.
I love seeing how they differ. And one boy even wore his t-shirt to school the next day.