IME Hongi cannot stand other fish that look like them. I had a brawl in my tank the other night. 2 hongi vs. 1 Metriaclima Zebra Long pelvic. Not fun. Lost 1 hongi but the Zebra has some damage. IMO I would not mix 2 that are the same genus species name unless they look unalike. For the fear that you would lose a lot of fish. But thats just my Opinion. Mbamba and Hongi look very alike except for the yellow and orange.
i had both in the same tank, got rid of the yellow tops the other day due to aggresion on the yellow tops behalf, the only reason i had them was cause they where mislabled in the LFS. but just wondering if i have pure hongi babies or i could have hybids, i did have 2 female hongi to my on male now 3 female on male