Koi. Nail master. Amsterdam. Koi is a nail technician providing manicures, pedicures, and gel-polish treatments. She delivers tidy, lasting results in a welcoming setting. Nail master. Amsterdam. Koi is a nail technician providing manicures, pedicures, and gel-polish treatments. She delivers tidy, lasting results in a welcoming setting. Nail master. Amsterdam. Koi is a nail technician providing manicures, pedicures, and gel-polish treatments. She delivers tidy, lasting results in a welcoming setting.