[canadawest]

I've read that you should rinse with seawater and not fresh water as well, as the fresh water will irritate the nematocysts to cause more pain.

With that said, I agree with Troy that tank water is probably not the best rinsing solution, so a better option would be a batch of freshly mixed saltwater.

Jellyfish stings are supposed to be very similar mechanisms, and according to the diving info I've read vinegar is supposed to help neuralize the sting as well as 50/50 rubbing alcohol/water mix.

From the diving treatments I've read they almost all suggest against topical creams or ointments like cortizone or lidocaine as they can aggrivate the nematocysts more even if it does reduce the immediate pain.

Apparently a regular anti-inflammitory or antihistamine will help reduce the swelling.