Thats great advice - dont be impatient like I was. Take him up on it. Dont add any more fish EVEN IF YOU DONT CARE if thoses particular fish get it or not. This is because as long as there's a host in the tank for the ick, it will live on. Let your tank purge itself and enjoy inverts. Take time to plan your fish choices, watch and learn as your tank matures. I know 90 days seems like an eternity, but once your Real fish are in there you'll want everything perfect.
Besides, I enjoy my shrimp/crabs/dusters/stars/snails/etc more than I enjoy my fish. Not only will the ick die off in this time, but the water will become much more stable. The water temp wont be so high after the hot summer anyway (at least here in the northeast where its been 95 for 2 weeks!)
Good Luck