The fish release chemicals that inhibit growth. The use of waterchanges add not only fresh water to the tanks, but also helps remove this hormone as well. Thanks for checking out my Why do Waterchanges help grow baby rainbows grow? videos. If you like what you see or hear rate this video or add a comment. Ask me questions. For more video, Live chat and custom user profiles to show off your planted tanks planted, reef or other fishtanks, check out www.fishtanktv.com