I cohabited a single male jack dempsey who was roughly 6”, two delhezi bichirs who were 5-6”, and a single full grown pictus catfish in a 75 gallon tank. I had absolutely zero issues with aggression or water quality. I later had a leopard bush fish, three African brown knives, the male jack Dempsey, and the two bichirs, the pictus catfish was moved to a larger tank. I believe that this was the upper limit of what that tank could have in it but I was comfortable with it and monitored the fish closely. There were absolutely zero aggression or water quality issues with once a week 75% water changes. I was very lucky to have a very mild Jack Dempsey, he was never aggressive to any of my fish even other cichlids. The only time he was aggressive was when he spawned but even then he was relatively mild. Cichlid temperament varies so much that it is impossible to say what your jd will be like.
That was a lot of info so I’ll give some final thoughts on your stocking list.
I would warn against having two jd’s, if they turn out to both be males you might have aggression issues between them, if they turn out to be male and female they will get aggressive with the other fish once they inevitably breed. Stick to one jd as a centrepiece.
The pictus catfish will hide most of the time if given a place to, having just one pictus catfish in my opinion won’t suit your tank. They really shine in a group, but a group deserves more space in my opinion. There are better solo catfish species imo.
The ropefish and bichir would work together with the jd. Add hiding spots and target feed them if necessary.
This is all MY OPINION based on what I’ve seen in MY EXPERIENCE. You may get an a-hole Jack Dempsey that attacks everything, in that case there isn’t much you can do.
I would have the rope fish and bichir with a single Jack Dempsey and maybe play around with different dither fish and see what works.
Best of luck!
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