They don't like them other than to eat. I made the mistake of putting hornwort in an African Cichlid tank. Constantly had little green things floating around the tank, and my filter intake was a freaking bush. Cichlids prefer caves to live in. I'd look into Texas Holey Rock if I was you. You can find some nice pieces here: http://holeyrockoftexas.com Or, just go to PetSmart and find some nice decorations with lots of caves in them.
If you mean what do they like to eat, don't feed them live plants. Get a zucchini, freeze it, thaw it, and slice off a piece. Anchor it to the bottom of your tank, and let them nibble on it for a few hours. Freeze the rest again. The freezing-thawing process softens it up a LOT, and that makes it easier for them to eat. Mbunas are mainly herbivores, so they'll need a lot of vegetable matter in their diet.
