I did quite a lot of research on loaches recently in pursuit of a solution to my snail problem. I even joined loaches.com forum. They are quite convinced that clowns and Malawi are a bad mix, you might want to read their article. They say clowns need max pH=7.0, attain a maximum size of 12 inches and should be kept in groups of 5 or more. Also that Malawi are way too aggressive for clowns.
I was actually looking for a different loach to keep with Calvus from Lake Tanganyika. (Calvus are very calm and quite timid.) Even though I found one that liked a higher pH and less water flow than the usual "river" loaches, after exchanging posts with lots of people knowledgeable about both fish, we concluded that even the Calvus, when adult, would be too aggressive for both fish to thrive when kept with loaches.
My conclusion was: it can be done, but the loaches won't thrive.
Barbie was one of the Cichlid-Forum posters who responded in the General Aquaria forum and helped with my decision.