You do know that adding 'cleaner' fish and 'cleaner' snails does not do anything to make the pond cleaner? Some species may be detritivores (consuming dead plant matter for the the most part), but they do not consume feces. Adding them will actually contribute to the bioload in the pond, making it dirtier, faster. Many people new to the aquarium hobby toss a few common plecostomus into their tanks in order to make it 'cleaner', and end up with a bigger problem then they had (overloaded aquarium, and having a fish that grows to over a foot in length) A pond is somewhat different from an aquarium, but many principles still apply.
The Chinese high fin banded shark is definitely not recommended to toss in the pond. Why? The size they grow to over three feet in length. And as stated, they won't do anything to improve the health of the pond.