I will assume your friend knows what he is treating? I have used furanizole and kanaplex with snails in the tank but not shrimp. The furan was said to be harmful to snails, and I did think the population seemed much fewer after the treatment, so I would be careful. But it depends upon the problem and the best treatment, for the fish, even if snails/shrimp have to be removed.
Bacterial issues like columnaris and a few closely related issues are most effectively treated by a combination of furanizole and kannaplex. The furanizole is what actually attacks thee columnaris, while the kannaplex gets the furanizole inside the fish better than without. But furanizole will discolour the water, not in itself a problem, but I did notice a significant affect (negative) on plants; the swords withstood it, but less robust plants melted.