Personally I didn't do one and I didn't even run carbon, I also overdosed with the interceptor to be sure it killed the red bugs because I was using expired interceptor tabs, But I wouldn't recommend not doing a waterchange because I'm sure it would be better, The only affect I noticed was my pod population lol I had piles of pods in a couple dead spots in my tank, I bet it wiped out every pod I had in there, I had to buy more pods online to seed the tank again, But there no was I'll affects on fish or coral and I just continued with my weekly waterchanges.