I would like to keep a weekly 40 percent water change so no thanks
If this is the minimum schedule you can abide, then confining the size fish in your tank to to nothing that grows over 7" would be a reasonable goal.
Larger fish in that size tank, will overwhelm it with nitrate, leading to chronic HITH disease.
The last time I had Cichla, I picked up a few couple inch juvies , and they outgrew my 150 gal tank in about a year..
But my water change schedule averages 30-40% every other day.
The pair below would tolerate no other fish, in a 250 gal tank, they were somewhere between 16, and 20 ".