I had 5 happy redbellies for two years.One was attacked

My baby's got along fine for two year's . I even have one dempsy ciclid that lives with them they were on special and bought 20 for food a year ago and they let this on live for some reason?But 3 days ago i found one baby half eaten and his face ripped apart i was in tears but the only reason i can think of is that whene i bought them the pet shop told me to have lot's of plant's and logs so they don't see eachother often.I have a 125 gallon and the past 4 month's whene a plant wold come up i just pulled it so it was a little empty i have 3 huge logs.So the next day after the death i went and spent 145$ on plant's and gravel to beef it up.These fish are very special to me i don't want this to happen again.Any suggestion's?

 

I'm guessing the plants should help. How often are you feeding them? It might help a little to feed smaller meals more often.

-Chelle