Don't be too quick to medicate Shamu. Obvousily if you know they all have flukes, go for it. But from keeping my tetra tank for about 5 years now I've noticed that often when a fish weakens and dies (I'm very sorry to hear he didn't make it, btw

) it will exhibit symptoms of disease, but no other fish in the tank will get ill. I recently had a neon which developed white spots that looked like ich. I was really upset because I thought I'd have to dose my tank, but the fish died, and that was the end of it. My advice would be to keep a close eye for other fish with symptoms, and if they show them then go for the medication.