Ok now can anyone give me a decent ID? I assume they are juveniles... maybe not full color yet? And I will be adding more "cave" material and rocks .... for now I just want them calmed and learn about them. I have never had any of these unless the striped one is a convict but he looks different than what I have had in the past.
Ok now I can see a lot better what they are. The first two fish look to be jewel cichlids. The fish in the next 2 pictures are jags and some kind of peacock female. Honestly unless you have a huge tank I would ditch the jags. They get to 16" and are nasty fish. If they don't kill your tankmates they will eat them eventually. They are a large growing guapote from central america and are huge fish eaters. 3 especially can cause problems since one may get bullied badly.
I believe you could keep the jewels and peacock female(the one you thought was a convict) in a 40 and they should be fine. The only thing I could worry about is aggression between the jewel cichlids as they can be a little on the aggressive side so just watch for that. You could keep 1 jewel in a 20L atleast for a good while but I think a 3ft tank would fit them better.
There are defiantly no jack dempsey's in that mix if that is all the fish you got pictured above.
You may be able to add a few more peacocks of the same species. But because almost all female peacock cichlids look the same, finding the particular species without correct labeling is very hard. Adding any other largish fish would cause problems. You have a very unusual mix of fish so I cannot predict how the aggression will play out. I would not put the peacock in the 20 these guys like to swim. I think the jewels and the peacock should be fine in the 40 but the pleco will defiantly eventually need a bigger tank.. Common plecos get HUGE! I would honestly get rid of it unless you plan to upgrade to a tank in the 100 gallon range. These guys can hit 2ft and emit a MASSIVE bioload.