He did say don't, and not that being over cautious isn't a good thing, but in my experience of keeping fish, which is around 10 years or so, all be it when i was younger, is that there is not too many problems keeping a male in a community tank, in my experience, females tend to be more aggressive, but as i said that is just in my experience, other people may have different views, on the over cautious note, i think most people are, the guy in my local shop is trying to get me to wait 2 months after set up before i put any fish in, and constantly tells me im being silly going and and stoking up having only my tank set up for a two weeks,
this is me being over cautious, in the past i would set up have fish in straight away, only talking peaceful community species here, nothing fancy, i know you can specialise i know you can have problems, i for one,in the past have never tested my tanks for nitrates or whatever.
I have bred angles guppies platys, some killies really successfully and had moderate success at shows too, and im not not really that knowledgeable, but its not rocket science, i strive to make my tanks as close to the habitat as the fish i keep, this is me getting back into a old hobby, mistakes will be made am sure, but is that not part of the learning curve ?