Use a biofilter, like 30% coco and 70% clay pebles, i`m use the foam glass for biofilter in dwc. I`m stopped using clay pebbles for my new start in dwc with bacteria. My biggest problem in dwc - root root for northern light and afghani ibl strains. When I added bacillus amyloliquefascience(diy hydroguard), glomus intraradices (diy Xtreme gardening Mykos, Orca, AN Piranha) and Pseudomonas Koreensis(DIY Xtreme Gardening Azos) in my garden root rot stopped forever. Don`t use Ammonia Nitrogen for Glomus. He don`t grow. Other Raw Salts working good for all types of bacteria.