Those are neat black guppies in the photo. (Don't know why, I had to copy the URL, past it above and cut the last part off. That took me to a directory, which offered the shot of black.) Would those be 3/4s blacks? Are your just youngsters of that strain or a pet store version which will not develop such tails?  I hope the delta tails develop. :)

See
 http://www.gcca.net/fom/Archocentrus_sp_Honduran-Red-Point.htm

That article suggests that those fish are not a strain of convict cichlid, but they sure look like them to me. My convicts, like the Honduran Red Points began breeding at 2 inches and were still breeding several years later when they were 4 and 6 inches long. They were not hospitable to tank mates in the mere 20 I gave them.

While small livebearers may not be a regular part of their diet, I fear putting them in any tank with guppies would start that trend. Some cichlid people use small fish (I'm sure guppies have been used) as target fish. The cichlids focus their aggression on the guppies rather than each other, for a little while anyway. :(

Dither fish are a little different - they swim high in the tank and encourage shy fish to come out of hiding. Sometimes the line between dither and target gets blurred. Never use fish you want to breed or show for dither fish.

In a 20-gallon or larger with lots of hiding places, the guppies might survive well fed Red Points, at least until they spawned.

Does it seem like I really think putting guppies together with most cichlids (and certainly all Central American cichlids) is a not a good idea? ;)