Thanks, I appreciate the info. I'll check KH this morning to make sure it hasn't dropped too far. Water from the tap has a KH of 7, so hopefully I'm still OK.
My long term plan is to be able to do 50% water changes (hence the 40G holding tank for the 75G) daily. And I'll wait til ammonia and nitrites drop to 0 before adding any more ammonia. The Dr Tim plan I was following had me adding ammonia on Day 1, Day 3 and Day 6, which I did. I've tried to keep the overall ammonia under 4 ppm, so I didn't add as much as they suggested. Their plan also calls for adding the fish on Day 9, so I think I'll just throw out the plan and go with the Shan 2 step plan above.