I would guess water movement over the surface of the substrate can increase the ammonia consumption... so as little as a wave maker could make a big difference???
@Rusty_Shackleford Dr.Tim H., the inventor of "bacteria in a bottle" (with the correct bacteria), also worked to create the biowheel filter. My only objection to that is all the gunk builds up & slows or stops the wheel. Since the biowheel BB is mostly on the surface layer after the wheel fibers are clogged (where the oxygen is plentiful). The "other gunk" is more like layers of biofilms (which Dr.Tim also worked on). If you clean or replace the biowheel, you lose that BB. But there should be plenty in the filter media to recover pretty quickly. I just don't need another place to clean or replace, lol.
I have some Aqua Clear filter sponges that are 20-30 years old & still going strong. Squeeze & rinse in running tap water doesn't kill off all the BB. But like I said, I like 2 filters on most tanks & stock fairly lightly.
As for substrate, with plant roots or undergravel filter, those are a great place for BB. But with only an HOB or air driven sponge filter BB are only on the top part where there's enough water movement to sustain much BB. No water (& oxygen) movement & bad things can happen. I bought an emergency battery operated air pump when I raised young discus in a bare tank. We had power outages that could last for several days. Luckily, I never had to use it. My other tanks had many plants, so I didn't worry as much. But I did do small splashy water changes to help, all my critters survived a 5 day outage with no working heaters either but we had some fireplace heat. Others were not so lucky
