I recently purchased a Penguin 170 for my 29 gal. tank which has a bio-wheel. My quesion is, is this good enough if I plan to place Malawis in it after my fishless cycle is complete?
No a 29 isn't really big enough, especially for the collection of mixed aggressive fish you have. It's nothing to do with filtration and everything to do with aggression, territories and tank lengh.
With regard to your actual question . . . I think that the 170 is a big enough filter for a 29 gallon. I have a 125 and it was doing ok and then I added a ACmini for a little extra help. Basically, I think the 125 was enough so the 170 should be plenty.
