Howdy! Interestin' mix of cichlids from around the world. The fish ya have will outgrow the 30 in no time; the sooner ya can upgrade to the 90 the better to prevent stunting the fish's growth and to reduce stress and aggression as the fish grow. Make sure yer tank is broken up with plenty of clay pots, rocks and driftwood to allow plenty of hiding places in case of aggression, and continue this when ya get the larger tank. The dempsey wil get 8"-10", the cons 3"-6" depending on sex, the yellow labs should max around 5" or a little more on average, and the acei around 6" or so on average, so ya can see where yer gonna have way too much fish for that tank soon, probly sooner than ya like. And that isn't even includin' the dragonfish, the pleco and the catfish.
A lotta hobbyist's will recommend not mixin' cichlid species from different geographic regions as a general rule, myself included. That said, it can be done with careful selection of species that are not extremely aggressive and that do not differ too greatly in adult size. The species of cichlids ya have can be managed together. The dempsey and convict are of Central American origin, the acei and labs are from Lake Malawi in Africa. All of these are likely captive bred, which reduces concerns about differences in water requirements. My biggest concern with the cichlids is the cons. Not necessarily individually, but if ya have a male and female and they pair up you'll have issues.
Assumin' ya have one of the species sold under the generic label of "common pleco", the pleco will get 10"+. IME most cichlids ignore plecos for the most part, unless the cichlids are spawning. I won't conjecture on the catfish, there are too many species offered for sale. But some species do get extremely large.
The dragonfish (Gobioides broussonnetii, more than likely) is a problem. It can reach 24"+, though 14"-18" is more typical in an aquarium. It requires mid to highly brackish water for long term maintenance and would prefer a sandy substrate. It will likely get picked on by the cichlids as they get older and probly will not be able to compete with them (or the catfish) for food. In the best interest of the dragonfish, I suggest findin' it a new home. At least leave it in the 30 after ya move the rest of the fish to the 90 when ya get that tank. Target gettin' it a larger tank and adjust the water conditions in the 30 to meet it's needs in the meantime. The dragonfish will eat better and show brighter colors in brackish water, as well as living a longer, healthier life.
WYite