Put in 8 Koi and 5 goldfish for a few days.. now I'm catching them and returning them to the 240gal holding tank next to the big tank. Cool to see them interact with the reef stack but they are not as agile as SW fish, they are scraping up their heads on the sharp reef rock... they prefer smooth boulders in their pondsLol they will not be happy having to move out of the tank again.