This is the difference in substrate between the dirt and the non-dirt side. You have to use good substrate in your tank. Thanks for checking out my 75 Gallon fishtank with half dirt and non dirt in the substrate 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