I did quite a bit of research before setting up my tanks, including into all the standard practices employed by most people here.
I also found numerous viable exceptions to several rules and a strong indication that the compatibility of tank mates has more to do with a case by case basis than it does any rule of thumb, so to speak.
One of my best friends bought a used reef tank with two yellow Tangs and one blue Tang, if you know the standard practices of keeping marine aquariums this type of combination is said to fail 100%, many people he informed of his tank set up, which had been stable in a dentists office for 17 years, told him he was lying. Eventually he has people come over just to prove it.
That is just an example of how rules and standard practices tend to have exceptions.
I found several cases of people keeping tanks with Gouramis and Bettas successfully, and I found several cases where an individual gourami or betta killed tank mates.
I found several variables factor into tank compatibility, for example you cannot keep some types of fish together in small numbers because of aggression. In the case of gouramis (I am into anabantoids) a male cannot be kept with fewer than 3 females and is best with at least 4-5. For several reasons the behaviors change with different stocking densities, too few fish, or too many both lead to problems.
Anabantoids are often highly territorial, even the females, given a tank with many hiding places and plants they will each claim an area that they will tend to return to. Because of this a profusion of hiding places has even been employed by some breeders to allow females to escape the violence of a nest guarding male, while still living in the same pond or large aquarium as the male. This can allow a person to leave a female in the spawning tank while they are at work, and then retrieve her when they come home from work, whereas in a bare tank she would be quickly seen and killed before the person has come home from work.
So while I am likely to be flamed strongly, I am aware of the standard practices of Betta keepers, as well as those of keepers of many anabantoids and other types of fish and even marine organisms.
It occurs to me that some of the ingredients on the very food people feed these Fish include other fish and small organisms, I've been feeding my fish fruit flies for example and fish is often an ingredient of fish food. I think there is a bit of a double standard for some people in regard to their set of ethics surrounding how they keep and care for their fish. I am autistic, btw, being an aspie, so consensus means little to me, precedent and data means far more, so does experience. I am gaining my own experience and won't let consensus prevent that, however I am letting it guide it.
As I said, if there is a problem I'll post it, but I'd even wager that it is possible to set up a peaceful community tank with two males in it, if you got the set up and and other members of the tank right. From what I have seen each fish has their own personality, which falls into a standard range, exceptions to their standard behaviors are rare, but so is experimentation among keepers of these and other fish.
I have a couple of empty containers ready to receive the male if needs be, and have been observing the tank, which has had a male in it (with females) for over 3 weeks now without incident.
An interesting thing I found online is a correlation between aggression with higher temperatures in at least some anabantoids. This would make a nice experiment for Bettas that someone has likely done already, correlating aggression with temperature. I wish I had more data, opinions don't mean so much to me. If you tried a male in a community tank and it was a problem, then tell me about it, how long did it take before there was a problem, what size was the tank? How many of what kind of fish were in it? What was the temp and what were the foods?
What was introduced when? These things mean so much to me, but saying don't do it doesn't mean anything to a man like me, even saying you tried it and it didn't work is worthless to me without details like what the tank was planted with and how many hiding spaces there were.
Last edited by Josh Young; 05-20-2010 at 10:38 AM.