BB are *attached* to pretty much everything but the water LEAST of all - gravel, ornaments, your mechanical filter & it's media the most. Large water changes will dilute dilute any unwanted/unhealthy substances in the water (**assuming** they're done properly with dechlorinator, Prime etc). Hubby has an overstocked 125g and is a chronic overfeeder("I gave them more because there's so many and they are acting SO hungry"[emoji37]) and I try change out 50-75 at least once a week, twice if I can. He still loses the odd fish here and there but the Kribs, Swords & Platys are breeding so I figure I am doing something right[emoji57]