I house my Bleekeri Small Spot breeding pair in a 6ft 100g tank with a female JD, male convict, and a couple severums. Things are great. The pair have never been closer and still breed regularly. The lenght of the tank allows the pair to mitigate their spousal abuse problems common with Bleekeri and the aggression of the tank is kept in check by the JD (who runs the tank but holds a somewhat humble attitutde).
I think the species-tank debate should be kept to a different thread topic if, one was so inclined to engage in a productive and useful debate regarding this issue. Personal experience goes a long way but without supporting evidence, for comments like "don't you think the fish will be much healthier", the argument loses significant validity. What 'I think' and what reality is for the fish is, may in fact be two separate things, we can't ask them. The health of the fish I have, even though they are 'mixed' is far greater than what it would have been had I not 'rescued' them from worse conditions. Keeping in mind that the 'wouldn't these fish be better off if we just left them in the wild and banned all aquariums' debate is never brought forward.
my 2 cents.