Best treatment for Ich in UK?

We recently got a new common goldfish to go with our older one and we kept checking for Ich as we know it is classic 'new tank syndrome' everything seemed fine, then after over a week, we noticed Ich was present. We are currently using interpet gold disease safe which is so complicated about the measurements! Anyway we started treatment ASAP (monday 24th) and this treatment is supposed to be a one off and to repeat after 5 days if it doesn't work.

However, my oldest fish has now got Ich on his gills which has me in a panic and he's flashing so the parasite must be irritating him. His fins are very blood streaked too.

I don't want to lose him cause he's such a strong fish....he was rescued a couple of years ago from my cousins who kept taking him out the tank and he didn't have a filtered tank then either. Even after a 7 hour journey in a van when we moved he didn't get stressed!!

Both fish are quite active and still love their food. Apart from the spots and the older fishes' little bit of flashing, they haven't changed behaviour.

What do you think? And can anyone suggest a better treatment for Ich???

[seattlemom2plus]

How are your fish now did you get rid of the ich?