Most BB are in the substrate unless you have some serious fish load or a canister filter... You can remove hang on backs completetly from your tank and nothing will happen..
Trust me, ALL of my tanks that do have hang on backs i clean the filter floss in tap water with chloramine in it and i clean it harshly, and often and nothing happens to my tanks and no ammonia shows up.. BUT if i change the substrate to a different substrate which i have done twice.. Ammonia spikes like crazy.
Take my 27g tank for example, had a 30g hang on back filter on it, i changed the substrate completetly to floramax midnight black from the clown puke blue rocks i had.. Ammonia went through the roof to 8ppm.. My filter did nothing to help it. My 44g Pentagon used to house 8 discus and neons and ect.. No ammonia issues and i even had a huge canister filter on it which i do only clean with fish water not tap.. I changed the substrate from brown pebbles to floramax substrate and boom i had ammonia problems in that tank which sucked..
Soo i will say it again BB are more prevalent in the substrate vs the filters
Dont believe me ? Try it youll see, remove the filter and watch nothing will happen if you have an established tank