In a 75 gallon you can do juvenile groups or breeding pairs of any parachromis species, with the one caveat that dovii will need more space as they approach a foot long.
Of course pretty much any pair of parachromis is unlikely to last long if they grow up together, pair up early, and you feed them both together. Even if they are the same size when they first spawn, the female's growth will slow dramatically even if she eats the same amount as the male, since her body invests so much in the production of eggs rather than growth. Once there is a noticeable difference in size, it will just get worse because the male will now get even more of the food and plus she'll be constantly using energy to heal from his inevitable aggression. The next thing you know, he's twice her size, he is ready to breed again before she is and beats her to death, you have a show male but no pair. I believe this will happen eventually for most pairs of parachromis kept alone in even a very large tank. I learned this the hard way from my first pair of managuense.
Here's what works for me with parachromis: I have a pair of 8" managuense that breed regularly in a 55 gallon. This is not optimal but previously I even had the pair breeding in a 30 gallon (3' long) tank. They are nearly identical in size and they raise fry together fantastically for about a month each time. Usually around this time the male loses interest in the fry (but doesn't eat them) and starts abusing the female to breed again. Once I see them fighting I separate them with a see through divider and feed the female better than the male to try to keep the pair evenly matched so that he can't kill her when they do fight.
Plenty of people won't like me keeping them in such small quarters and slowing the male's growth, but if you take care of the water decently Parachromis species will be very active, look great, and spawn plenty even in not so huge tanks.
So my vote for your 75 gallon: a pair of jags or red tiger motaguense
Here is a link to an aquabid auction for a pair of red tigers:
http://www.aquabid.com/cgi-bin/auction/auction.cgi?fwcichlidc&1170733267
I would buy them myself if I had space!
Of course pretty much any pair of parachromis is unlikely to last long if they grow up together, pair up early, and you feed them both together. Even if they are the same size when they first spawn, the female's growth will slow dramatically even if she eats the same amount as the male, since her body invests so much in the production of eggs rather than growth. Once there is a noticeable difference in size, it will just get worse because the male will now get even more of the food and plus she'll be constantly using energy to heal from his inevitable aggression. The next thing you know, he's twice her size, he is ready to breed again before she is and beats her to death, you have a show male but no pair. I believe this will happen eventually for most pairs of parachromis kept alone in even a very large tank. I learned this the hard way from my first pair of managuense.
Here's what works for me with parachromis: I have a pair of 8" managuense that breed regularly in a 55 gallon. This is not optimal but previously I even had the pair breeding in a 30 gallon (3' long) tank. They are nearly identical in size and they raise fry together fantastically for about a month each time. Usually around this time the male loses interest in the fry (but doesn't eat them) and starts abusing the female to breed again. Once I see them fighting I separate them with a see through divider and feed the female better than the male to try to keep the pair evenly matched so that he can't kill her when they do fight.
Plenty of people won't like me keeping them in such small quarters and slowing the male's growth, but if you take care of the water decently Parachromis species will be very active, look great, and spawn plenty even in not so huge tanks.
So my vote for your 75 gallon: a pair of jags or red tiger motaguense
Here is a link to an aquabid auction for a pair of red tigers:
http://www.aquabid.com/cgi-bin/auction/auction.cgi?fwcichlidc&1170733267
I would buy them myself if I had space!
- glad to hear that!!!!!!! 
- I'm getting one of his males, it should be here this Saturday! 
