I have a 20 gallon tank with around 6 tetras in it and was thinking about getting gouramis but have had some trouble with them b4 the male blue was eating the female
would it be better to keep only a couple of females or are there some species less agressive toward each other
I prefer to keep one gourami per tank, no matter what kind. I had problems with blue gouramis with eachother, and since then I would rather just not have the hassle of them harassing eachother. Some say dwarf gouramis are better, and pearls certainly are OK with eachother. You might want to consider a dwarf type for your tank, as it will allow you to have other fish too (some of the other gouramis get to 6").
My experience if you crowd the males, such as Colisa lalia, you wont have problems due to territorial disputes are irrelevant considering there is no way the fish can defend there territory sorta like with cichlids, it works.