Clean up is actually very important in this case. My turnover rate is 45 times the size of the aquarium (1800 GPH
in a 40 gallon breeder) and sometimes the poop stays at the bottom. That's a lot of flow and I still rely on my CUC.
Also, it's hard to say much here because the OP has not said anything about his/her aquarium. Certain fish are just heavy poppers and their poop will stick to the bottom. If all the OP has is small fish then technically a good flow should take care of the problem. But we simply don't know it for fact.