Good article - you're on a roll!
"Common" fish are widely available because they tend to have the characteristics of great aquarium fish: hardy, mix well with other fish, colorful, easy to breed, etc. What's not to like about keeping them, even if you are an "advanced" aquarist?!
"Rare" aquarium fish are often less suitable aquarium residents. Ex-Cichlasoma beani, which was the hold grail for a passing minute, comes to mind. It's been in and out of the hobby a few times. Why doesn't it stick? Well, it's a big, brown (albeit sometimes with a honeycomb pattern), mean as sin cichlid that tends to get bloat. In the rush to acquire the holy grail, how many people were really prepared to raise them for life? Had worked their way up to keeping such a demanding species? The number of adults in the hobby answers that question...
The decline of quality LFS has led to the rise of many really good online sellers. The good thing about that is that literally hundreds of common and rare species are almost always available to anyone with a few bucks. The downside is that if just about anything is available, nothing seems rare of unusual anymore...and people are always on the quest for rare.
I'm a big fan of keeping what you like because YOU like it. Which is why my fishroom is full of the fish that I like, including many common ones. I'm always surprised when no one will spend $2 for a bag of rainbow cichlids or kribs or whatever relatively common fish in our club....when only a handful of folks in the club have BAP points or successfully bred them. They're great fish. Common or not
Matt
