I think you're confusing uneaten feed and faeces with mulm and bacteral film. The uneaten feed and feces is detrimental as it can go anoxic and produces competing heterotrophic bacteria. The bacteria you want is an autotroph and is aerobic. Unfortunately the heterotrophic bacteria multiplies much faster so you don't want to produce condusive conditions for it like a build up of uneaten feed and feces.

The mulm is neutral (except when it clogs pipes and filters), and the biofilm is produced by the bacteria to adhere to surfaces and protect the bacterial colony.

Over cleaning of an aquarium can elimnate the good bacteria but some cleaning is in order,

Last edited by Cecil Baird1; 02/10/16 10:21 AM.
If pigs could fly bacon would be harder to come by and there would be a lot of damaged trees.