I have three male Yellow Rock Kribs in a 120 gal. They are tough & very colorful little guys. The Rock Kribs can hold their own against most Mbuna. I keep Red Zebras, Kenyi, Rusties, Socolofi, Trewavasae, Zebra Chilumba & Afras with them w/ no real problems. I also keep a few predator Haps in the mix; again no issues. The Rock Kribs are too quick for them. I don't see Rock Kribs for sale often in my area. I'd like to eventually buy a few females. Here's a couple of pics.