I'm fairly certain a Midas needs a larger tank. The Acaras are a way better species for your tank, will still be interactive, attractive, and comfortable for life in that tank. As
J
jaws7777
says... larger cichlids fart out nitrates LOL... Seeing a large fish in a small tank is kind of depressing IMO.
I'm right on board with Jaws also in regards to choosing fish - ultimately do YOU find bichirs interesting? Do they appeal to you? You might end up with an individual that isn't very active... will you still think it's cool to watch and stare at? I know the answer for me (hells yeah) but not for you.
I worry you'll get bored as you mention because in your posts you keep jumping around as far as your interests go. I look forward to seeing you settle down in your decision and get excited about planning the setup to make it successful. Getting a tank started can be tricky until it finds a certain equilibrium.
I also like the 3 upper jaws with the acara plan.
Ropes are awesome but I think they're best for a planted tank (or at least heavily fake-planted.
)
If you don't have a strong preference in looks for the polys, then go for activity: Senegal, Delhezi, Polli. Buettekoferi are known to be hiders, so get one only if you think it's really cool looking IMO.