Pretty much all commercial farmed fish is 'dirty', but so is most commercially raised meat.
I don't like Tilapia because it tastes bad a lot of the time, like pond water.
Having grown up eating fresh-caught centrarchid fish in the Great Lakes area, perhaps I am just picky.
We eat a lot of fish, and we just spring the extra $ for sustainable-harvest, mostly northern Pacific, species. (I do occasionally eat amberjack when I'm on the southern coast, but that is too laden with toxic metals to eat regularly even when it is sustainably harvested).