40 Gallon Breeder Electric Blue Acara

[Mallard]

I have this 40 gallon breeder (36"x18"x16") and I definitely want to stock it with an Electric Blue Acara. I was wondering if I could fit one or two more of these cichlids (not each, but total) and which would be the best choice(s):
-Firemouth Cichlid
-Keyhole Cichlid
-Festivum Cichlid
Or, would it just be better to have it alone with some dither fish? If there are other cichlids other than the ones listed that could fit and do well with the Acara and that stay around 6" please let me know!
Also, if it is housed with other cichlids, how should I go about in making the hardscape and territories? Is it as simple as making a cave for each fish? Although I hear about markers and line-of-sight breakers and am quite confused as to what exactly those mean. Will plants work as those breakers?
I have kept Bolivian and German Blue Rams in the past and am familiar with the nitrogen cycle and the risk of aggression in keeping several cichlids in the same tank. Any help and advice would be greatly appreciated!

 

[Byron]

More than one species of neotropical cichlid in the same aquarium is not usually recommended unless the tank is very spacious. At 8 inches, the Blue Acara (Aequidens pulcher) is not a small fish, and a 40g is a very confined space (fine for this species) so I would not have other cichlids. Aquascape should be sand, rock caves, chunks of wood, dried leaf litter. Plants would tend to get dug up, so floating will provide the benefit of shade (important) and water qualiity. A pair would be OK. Smaller fish tend to get eaten apparently.

 

[Mallard]

More than one species of neotropical cichlid in the same aquarium is not usually recommended unless the tank is very spacious. At 8 inches, the Blue Acara (Aequidens pulcher) is not a small fish, and a 40g is a very confined space (fine for this species) so I would not have other cichlids. Aquascape should be sand, rock caves, chunks of wood, dried leaf litter. Plants would tend to get dug up, so floating will provide the benefit of shade (important) and water qualiity. A pair would be OK. Smaller fish tend to get eaten apparently.

I see thank you for the feedback!