aqua_holic
Aquarium Advice FINatic
Kind of. The efficiency of the bacteria is a function of pH, which is why people with low pH can have trouble cycling. Also why it's suggested for some to raise the pH with baking soda during fishless cycles. So the bacteria colony of a tank with a pH near 8 will be much smaller than that with a pH of 6.5, yet do the same job.
Too, the turnover rate plays a role on the colony size. The faster the water is turned over, the lower the standing ammonia concentration entering the filter, and the less bacteria will be present. A slower turnover rate means more time for the ammonia to accumulate, which means a larger colony is needed to process it all. That's the fundamental reason why HOB filtered tanks need a higher turnover rate than canister filtered tanks - to make up for the lack of media they hold.
Too, the turnover rate plays a role on the colony size. The faster the water is turned over, the lower the standing ammonia concentration entering the filter, and the less bacteria will be present. A slower turnover rate means more time for the ammonia to accumulate, which means a larger colony is needed to process it all. That's the fundamental reason why HOB filtered tanks need a higher turnover rate than canister filtered tanks - to make up for the lack of media they hold.