As you know, we spend a fair amount of time snooping around the scientific literature online and in libraries, looking for tidbits of information that might fit nicely into our fascination and evolving technique with blackwater- and now, brackish- aquariums. It's a pretty fun pastime, really- and educational, too!
And one of the interesting things about sifting through scientific stuff is that can occasionally find bits and pieces of information which may not only confirm a "hunch" that you have had about something- these data can sometimes send you into an entirely new direction! (I know it does!)
As a lover of brackish water habitats, I've spent a lot time over the years researching suitable fishes and other aquatic organisms from this environment for aquarium keeping. Now, sure, many fishes can adapt to brackish water conditions, but I'm more fascinated by the fishes which are actually found naturally in these environments. And it's always interesting when you can find our that a fish which you have previously dismissed as not having typically come from this actually does come from it naturally!
One of those happy "surprises" is our good friend, the "Endler's Livebearer", Poceilia wingei.
This popular fish is widely kept under "typical livebearer conditions" in the aquarium ( higher pH and harder water). However, there are a number of wild populations form their native Venezuela which inhabit mildly brackish water coastal lagoons and estuaries, for example, Laguna de los Patos, near Cumana, which has definite ocean influence, although it is far less salty than researchers thought it may have been in the past. And the wild populations residing there might very well be considered "endangered", or at least, limited.
Now, this kind of stuff is not "revolutionary" from a hobby standpoint, as it seems like we've known this for some time. And although the fish are most adaptable, we don't hear all that much about keeping them in what we'd call "brackish" conditions (like SG of 1.003-1.005). It's just interesting to ponder and get your head around. It seems to me like the brackish water habitat for this species has not been embraced much from a hobby standpoint. And I suppose it makes sense- it's far easier to simply give fishes harder, alkaline water than to "mess with adding salt" to their tanks for a lot of hobbyists. And, wild populations of these fishes are scant, as is natural habitat data, so indeed confirming with great certainty that they are still occurring in these types of habitats is sketchy.
In general he question about adding salt to livebearer tanks has been debated for a long time, and there are many views on the subject. Obviously, the ultimate way to determine if you should or should not add salt to an Endler's or other livebearer tank would be to consider the natural habitats of the population you're working with. Easier said than done, because the vast majority of them are now commercially or hobbyist bred- especially Endler's. I think the debate will go on for a long time! Yet, with the increasing popularity of brackish water aquariums, and the debut of "Estuary", we're hoping to see more experiments along this line for many different species!
Now, you know I've always been a fan of sort of "re-adapting" even captive-bred specimens of all sorts of fishes (like "blackwater-origin" characins, etc.) to more "natural" conditions (well, "natural" from perhaps a few dozen generations back! I am of the opinion that even "domesticated" fishes can benefit from providing them with conditions more reminiscent of those from the natural habitats from which they originated. I never will buy into the thought that a few captive generations will "erase" millions of years of evolutionary adaptation to specific habitats, and that re-adapting them to these conditions is somehow "detrimental" to them.
In the end, there are a lot of variables in the equation, but I think that the Endler's discussion is just another example of fishes which could benefit from experimenting with "throwback" conditions. I'm by no means anything close to an expert on these fish, and my opinions are just that- opinions. Commercially, it may not be practical to do this, but for the hobbyist with time and the inclination, it would be interesting to see where it takes you.
I look forward to many more such experiments- bringing natural conditions to "domesticated" fishes, and perhaps unlocking some more secrets...or perhaps simply acknowledging what we all know: That there truly is "no place like home!"
Stay adventurous. Stay experimental. Stay Bold.
And Stay Wet.