Originally Posted by thegabzzz
look, I know that you don't want to give people inaccurate information, but we have not stated any inaccurate information, some fish (like dmuddles) can do perfectly fine together. And one more thing, explain to me how Gouramis "dont get along" when the fish store have dozens of them in the same tank?
I'll answer your last question. Fish in store tanks are in temporary quarters, or so the store hopes. Store fish are often washed out in colour and pattern, due to severe chronic stress. They are in an environment which is far from good in several areas: usually overcrowded, inappropriate water parameters, lack of any decor (= in bare tanks, maybe a chunk of wood or something), bright lighting. This is all bad enough, but in many stores today they have central water systems that connect all tanks so something in the water in tank 1 is passing through every successive tank. And here I am not referring to possible disease, but pheromones. A slight digression on these.
Fish release pheromones which are chemical substances. We do major water changes to remove them, because there is no other way, and they build up until they are removed with water changes. Other fish read these signals. This is one issue behind aggressive fish; even if there is no physical interaction, the aggressor is sending out the chemical signal that "I am nasty, watch out" and other fish pick it up and it gives them stress. This is the reason I never recommend Betta with small characins; the Betta may or may not physically attack the neon, but it is sending out signals and the neon is picking them up, and the neon will be stressed. The same works in reverse; the neon is likely looking at the Betta as a good target to nip, and the Betta can read that even if no nipping occurs. All this is stress, and that--if you read the article I linked previously--weakens fish seriously. This is also the issue behind your gourami, which I'll come to momentarily.
Back to the store tank. Being in the afore-mentioned conditions affects the fish. Sometimes they become more aggressive. But often in such situations, because the shere number is overwhelming, they do the opposite and withdraw, behaving far differently from their normal behaviours. They "appear" to tolerate each other, but the fact is that they are under such severe chronic stress they simply can't do anything. This too is having an impact on their physiology. When we then buy these fish and place them in normal surroundings, they may "recover," or they may not. Or they may turn even more aggressive as a sort of backlash. The increased aggression is the fish's only way of dealing with frustration, it must just lash out. And all because it has been weakened and harmed by the prior environment.
It is true that within a given species, variance can be seen from individual fish. Science does not yet know why, but it does know that any stress-related issue can throw the switch inside the fish and cause deviant behaviour, which ever way it goes. If the fish is not behaving normally, chances are something is--or was-wrong, and the abnormality may or may not correct itself; usually it does not.
Now to your gourami. All male Gourami, every species, are territorial. Same as all male cichlids. It is in their nature. Increased stress may worsen this, or weaken it (and the fish's health with it). That it why we maintain one male with 2-3 females of a species like the Pearl Gourami or the Blue Gourami. The males will be territorial, and usually this means they view the tank as "theirs." In sufficiently larger tanks, it is possible to arrange territorial spaces for them, and sometimes this works, sometimes not. Same holds for angelfish. If you took the time to dig through the threads, you will find several from members who tried combining various gourami only to have them "suddenly" at some future point turn on each other, and I recall Inga lamenting how her gold gourami killed all the other gourami in the tank within a few days. This is not unusual. So the wise aquarist understands the fish's "normal" behaviours, and provides for them. This is the only way to ensure probable healthy fish. Because any deviant from what the fish "expects" is guaranteed to cause stress, and we know--or should know--where that leads.
Inga had her gourami "doing fine" too--until one decided it had enough of the artificial environment and took matters into its own hands--or should I say fins.
Is this beginning to make sense?