Yes most likly it was the Cichlids that did it. I have a 90 gl with 14 African Cichlids 3 of them being 5 inches in size and I cant seem to keep Plecos alive. Some Cichlids like the ones I have can only be with their own kind cuz of how mean they can get so I use big snails to keep the algae down and the ACs dont mess with them. If you have any more questions you can aways find me in my fish chat on Tuesday at 9 pm est chat.pethobbyist.com/login.php?room_name=Fish+%26+Marine+Life+Chat