Kusuri have now brought out Kusuri Masuizai Koi Sedate, which is not an anaesthetic, it is a sedation formulation based on 2-phenoxyethanol.
Using Kusuri Masuizai Koi Sedate sedation is still deep enough to perform minor procedures, such as ulcer cleaning and scale removal. 

Full easy to use instructions on every Kusuri Masuizai Koi Sedate bottle.

Starting dose 10 ml to 2 gallons of pond water in a suitable bowl. Then add extra Kusuri Masuizai Koi Sedate as required as temperature plays a big role in fish sedation. Having said that Kusuri Masuizai Koi Sedate is safe to use at any temperature.