The question, as I see it, is one of scope. If we assume a biotope tank is an attempt to replicate a specific natural marine habitat, then how narrowly should we define that? In other words, where does a generalized tank end and a biotope begin? Is it:
A tank representing a particular ocean or sea?
As regular salties know, all the livestock in “Caribbean Chris’s” tank is found only in the Caribbean Sea. In fact, Chris seems to regard the existence of other seas/oceans the same way one might the existence of Bigfoot or the Loch Ness Monster—with skepticism. But is his tank truly a biotope? After all, with an area of 1,063,000 square miles (or so Wikipedia tells me), the Caribbean Sea is a pretty sizeable body of water. Not to mention, many of the same species found there also occur in the tropical western Atlantic.
A particular tract of reef?
How about a tank holding only species from Australia’s Great Barrier Reef, the New Caledonia Barrier Reef, or the Red Sea Coral Reef system? Perhaps we’re getting closer to a biotope here, but these and other reef tracts still cover a lot of territory and are home to a myriad of species. Is that really narrow enough?
A particular reef zone?
Here I’m referring to zones such as the upper-reef slope, reef crest, reef flat, back-reef slope, lagoon, etc. If you choose fish and invertebrates from only one of these zones and create water-movement/aquascaping conditions to replicate that zone, would the tank constitute a biotope? Or, would you need to narrow the focus even further to include only specimens from that particular reef zone on a particular tract of reef?
A single coral outcropping?
When scuba diving, it’s great fun (I think, anyway) to pick out a small coral assemblage or outcropping and spend a few minutes observing the invertebrates and fish that call it home. These are also probably the easiest niches to replicate in an aquarium setting because they’re about as close as you can get with respect to scale. We could probably all agree that such a tank would constitute a biotope, but again, where does that line of demarcation actually fall?
The eye of the beholder?
Perhaps a biotope—like beauty—is merely in the eye of the beholder. If so, where would you draw the line? Let us know in the comment section below!
Photo credit: Sean Nash