A few things
1. his tank is overstocked to hell, he shouldn't have that many fish if he "doesn't have time"
2. he still needs to keep up on the water changes, especially with a stock that heavy. He needs massive filtration and at least bi-weekly 50% water changes to keep all of that healthy
3. the heat and salt method is super easy and super not time consuming. tell him to look it up because those medications rarely work.