Euryhaline brackish water fish, like scats, archers, GSPs, and monos, are able to adapt to changes in salinity more or less instantly. According to Schaefer (Aqualog), the only problem with sticking a scat from freshwater into salt water is it's buoyancy goes a bit off and it needs to readjust its swim bladder.
But the point is that these fishes live in habitats where the salinity can change very rapidly. If you think about how an estuary works, it isn't a gradual change from freshwater to salt water. What typically happens is there is a "wedge" of salt water pushed along the bottom of the estuary and a less dense wedge of freshwater at the top. Between the two there is some mixing, but not as much as you would imagine because differences in temperature usually cause "stratification". Certain fishes exploit this. If you go to the (brackish) Baltic Sea, you find the freshwater fish living in the surface waters and the marine fishes vertically below them in what is more or less seawater. In other words, you're in a boat on the Baltic and 1 meter below you there are some pike and roach, but 10 meters below you there are salmon and herring in the brackish water. Or something like that, anyway. The numbers and species might not be correct. But you get the idea. Anyway, an estuary is a bit like this, with a "freshwater" fauna at the top and a "marine" fauna closer to the bottom. At the Amazon, for example, various loricariid and doradid catfish spend their entire lives swimming back and forth in an estuary following the freshwater wedge as it goes towards the sea at low tide and works back up river at the high tide. They are scraping the mangrove roots for algae and catching small prey like shrimps and snails. If they time things wrong and get caught in the saltwater wedge though, they likely die, because their tolerance for salt water is modest. Conversely, sharks and rays follow the saltwater wedge along the bottom of the river to forage for things like clams and crustaceans, but if they got caught in freshwater, they'd also be severely stressed and likely killed if unable to return to the sea quickly.
Scats and other true brackish water fish are different and are able to migrate freely anywhere in an estuary they want, cutting through the different salinity wedges. Alternatively, if they have found a particularly good food patch (like a sewage outfall pipe!) they will stick around while the salinity rapidly changes around them. This is their niche, and what makes brackish water fishes uniquely able to exploit estuarine environments.
All this said, if your drip method works for you and you're happy with it... stick with it. Like in captivity is more stressful than life in the wild for various reasons, so anything you do to make their lives easier is worthwhile.
Hope this helps!
Cheers, Neale
Just one Question !!! What do you mean by the drip method is overkill? When I get new Brackish Fish what come from about 1.003-5 into my tank at about 1.010 I allways put them in a bucket and use the drip method.
