I'm looking for a good, large, gravel stirring species of catfish for a 150 gal tank with a 10" Tiger Oscar, 8" Pleco, and a 4" snapping turtle. The catfish needs to be large enough that the Oscar and turtle won't mess with it. All three creatures presently leave each other alone except the Pleco will clean the turtle's shell now and again. I wold like to find a species of catfish that will clean up after the turtle which is very messy. Any ideas?

I've got two Chinese sucking cats. They get to about 5 - 6 inches and they can hold their own pretty well.

You might want to look into a Amazon Red Tailed cat, they eat everything and anything and get pretty large (in the wild 4-5 feet 150 lbs) and can hold their own, I used to keep one with my Oscars and they did great.