hey mattawan I just sent you a big PM so I won't repeat it all here but just will say that the LFS where I bought them breeds them in a 75g with a school of yellow labs as dithers so I think they'd be fine in a 75g, but I'd stock something like giant dems, yellow labs, and something else smaller and less aggressive, like rusties - probably just 3 species given their size, but they don't seem to need the swimming length like aceis, so a 4' tank should be fine.
I didn't say in the PM but since it was brought up here, I think giant dems need to be the typical 1m:4f (or at least, just 1 male unless its a species only tank when 3 might work with enough females). I've got 2 males and while they keep to themselves at opposite ends of the tank now, they have gotten into spats before, and I expect I could come home one day and find one of them dead sooner or later if I don't remove one soon. mainganos I had a year ago, found one male (the dominant one, no less) dead out of the blue with no previous signs of stress after just a couple months. Albino zebras, took about 9 months but recently came home to find one male out of 2 vying for dominance killed, again no previous signs of stress (hiding/not eating/etc). I had noticed some fighting at times but it was never damaging until bam out of the blue dead fish. the giant dems are more peaceful but IMO its like skittishness like a skittish dog - leave it alone and it'll never bother you, but corner it and make it feel threatened or try to grab its food bowl and its likely to lash out and bite.
They are a great fish though. I don't have experience trying to mix mbuna and haps so I can't really comment, but my LFS has a display all male mixed african tank that includes a male giant dem, a male and female yellow lab, some other mbuna, haps, and peacocks, including a really nice large trout cichlid I remember being there a year ago when the store first opened at about half its current size. Also, a frontosa, which looked absolutely miserable hiding in the corner behind some rocks. I'll stop in again sometime and take some pics.
