Like I say, I'm thinking we write letters and send them by post... write them here, print them out, and then send them all at once. Bombard the RSPCA and they can't ignore us forever. I think the we should also send these letters to fish shops that sell dyed fishes to show them that people--a LOT of people--do care, and to fish places that do NOT sell them with a "THankyou for not selling dyed fish" note. That would encourage them to keep staying away from dyed fish.
However, if people keep selling dyed fish, they're going to keep selling them. Perhaps we ought to move for a disclaimer first--petshops have to have a sign on their tank telling people that these fish are dyed, how it's done, that it stresses out the fish and makes it sickly, and that it doesn't always last--kind of like the Surgeon General's warnings on cigarette packs. This would help keep people from buying them. Maybe we could even rent a few billboards to spread the ugly truth and open people's eyes about dyed fish. Once people stop buying these fish, then we can move for a ban.