Fungus (has been) in the lens....

Have an opportunity to purchase a Canon EF 200mm f/1.8L USM lens....owner said it had a "fungus". It has had some type of "treatment" and he indicated that there is NO effect on the pictures. Priced at less than $300. Not for sure the effect of fungus on glass and was wondering what some of the people here think about it.

thanks

If you don't want it, send me seller's contact info.