I 'm sure they will with some of the more mellow Rift Valley haps, Tropheus spp., some of the featherfins and such from Lake Tanganyika, angelfish, discus, many geophagines, some of the Madagascan cichlids, and some of the other more mellow CA and SA cichlids, and I can see them being really hard on silver dollars and other relatively large, mellow species. Larger plecos will do this as well. But CAEs and large plecos both learn pretty quick that most mbuna, pike cichlids, oscars, acaras and probably 95% of Central American cichlids including Texas cichlids, convicts, jack dempseys, red devils, the Vieja species, Parachromis spp., etc. etc. won't tolerate being sucked on. It's bad for the CAE's health. I suspect frontosas, most of the tilapiines, all the Hemichromis spp., and few of the Madagascan cichlids (especially Paratilapia spp.) won't take to it too well, either. A lot of these cichlids could kill a CAE with one solid strike, and the CAEs learn really quick that the cichlids don't play nice.
Honestly, if kept with the right tankmates with an understanding of they're behavior, they are fun fish to keep. They don't belong in probably 95% of hobbyists tanks, just like so many other fish whose behavior and requirements aren't understood and met. I'm not advocating anyone getting them just because they can, just like I don't advocate anyone getting most cichlids and many catfish just because they can. CAEs shouldn't be bought as impulse purchases nor for tank cleaning purposes, which unfortunately is why most are purchased. They need to be included in a well thought out stocking plan with their flaws kept in mind.
WYite