What else can I put with my African Cichlids

Update, turns out I have a total of 5 rainbows in the tank. Is it really necessary to take these out, as I've been told they are living peacefully in this tank for over 3 yrs...?Any comments.

You can leave them I would say.

Synodontis catfish are a good choice.

Some people seem to do well with a couple of bristlenose plecs - although you hear horrible stories of the plecs having their eyes taken out as well.
 
Thanks to all for your help!! I've added 2 Synodontis catfish and some artificial plants to help for hiding for the smaller cichlids. Gonna leave them alone for a while before making any other changes.
 
I'm sad to inform the forum that as I was warned, one of my red rainbows was massacred over the weekend. I found her while rearranging my rocks/shells. She was under one of my seashells with both eyes eaten and most of her fins nibbled off. I was heartbroken all day yesterday. I am moving my remaining 4 rainbows to another tank :(
 
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