Hmmm the LFS only had praziquantel in a product for treating dogs for tape worms.
The bloke that advises the shop on these matters said "use somthing like rapid white spot cure that has lots of malachite green"
I bought some but went home to dose the tank and there was no Oscar hiding on the bottom...looked closer and there were 2 looking for a feed.
I gave them some peas, the skinny one had one half (the other ate about 4)but still seemed slightly distressed even if looking lots better.
Shall I wait to see if he continues improving?