because hybrids are not pure blooded species. you put that fish in with another of similiar type and she will breed again and again, mudding up the gene pool even more.
some thoughts taken from articles on cichlid-forum reguarding hybrids that I happen to agree with, just give them a read, it never hurts to learn more
1. You may feel that the issues surrounding hybrids don't concern you, and for the most part that's probably true. You're not going to sell any fry and you don't care if your hybrid doesn't develop good color. But where it affects you directly is that a hybrid can seriously mess up your well thought out plan for a compatible tank. You just don't know what you're getting. How big does it get? Will it outgrow your tank? How does it behave? What fishes does it get along with? Who will the hybrid mate with, and will they want to mate with him? Or is it a her? How do you know your hybrid's grandmother wasn't a Melanochromis auratus and will someday seek to kill every other fish in your tank? You don’t.
There are just too many questions that can't be answered and questions without answers require luck, and of course then you gotta ask yourself: Do I feel lucky? □
2. When buying a fish, make sure that the fish you are buying is the fish advertised. If you do your homework, instead of buying on impulse because the fish looks really cool, this won’t be hard. The reason why this is so important, other than the necessity of knowing how to care for it, is to avoid purchasing or accidentally breeding hybrids. Why are hybrids bad, you might ask? Hybrids are bad for several reasons. First, they dilute gene pools for some really gorgeous fish. Let's say you want to purchase a M. estherae (Red Zebra). You are expecting a bright reddish-orange. But, these are often cross-bred, giving a diluted, washed out orange, almost pale pink. Or, if you wanted some other fish, imagine the same scenario. Furthermore, many Cichlids are only exported once or a few times, meaning that if we want to keep them in their original form, we need to maintain their purity. Also, in addition to often producing mottled or pale colors, hybrids may turn out sterile (which would actually be a good thing). Not to mention that most of the Victorian Haps are either extinct in the wild or endangered, which leaves it up to us to propagate these species.
OTHER VIEW:
3. The real abhorrence for hybrids amongst the cichlid crowd has more to do with hybrid African cichlids than with the American hybrids discussed so far.
Early in the cichlid hobby, many hobbyists would set-up an African cichlid tank with a bunch of rocks and a bunch of Mbuna. When a female was seen holding eggs or fry, they would be caught and stripped, but this procedure was easier said than done. Often the females would be left in the tank and the fry were left to their own devices among the rocks, frequently evading the adults which were poor predators to begin with. So the fry would often appear in the tank and their heritage was completely unknown. Sometimes the fry would not look exactly like any of the adult fish and they might be presumed to be hybrids. Other times, separate species would be seen spawning so the fry were known to be hybrids. In any case, this offended the sensibilities of the hobbyists who saw themselves as preserving these high priced fish. Now days we realize that even though these fish have a low fecundity, they are very prolific. We have nothing to worry about as far as the survival of things like zebras, Labeotropheus species and other Mbuna surviving in the hobby, yet the hybrid African cichlid is usually not welcomed at society functions. As easily as rift lake cichlids hybridize in captivity, how do we know that there aren’t several naturally occurring hybrids among them?
If you’ve stuck with this article this long, you should have seen how some hybrids are accepted at society functions while others are not. My contention is that there is a prejudice against hybrids that is not maintained in all cases and is totally arbitrary. If a hybrid can be readily purchased at a store, does that make it more acceptable than the result of a cross in a fellow hobbyist’s tank? Apparently so, unless that fish offends our sensibilities as the parrot cichlid does. I suspect that many hobbyists are unaware that they are supporting hybridization when they purchase certain fish, just as the proclaimed vegan is blissfully unaware that they are supporting the beef industry when they drive a car that has tires as well as many other items that include beef by-products in their manufacture.
B) I SIMPLY DO NOT LIKE HYBRIDS, NOTHING MORE, NOTHING LESS, JUST MY OPINION B)