Reefmonkey
Aquarium Advice Activist
I have found when I have kept brackish fish that many LFSs, and especially the chains (petco, petsmart) will be keeping young brackish species in pure freshwater. When I am putting the first brackish fish into a newly setup brackish tank, I plan ahead, set the tank up with just freshwater, then stock the tank. Every time I do a water change, I add water mixed to a little above my target SG, so I slowly raise the SG of the whole tank to my target over a few months. That's fine for the new tank, but I am always concerned about adding, say, a young scat that has been kept in freshwater to my established brackish tank, possibly causing osmotic shock. In general, if I had the extra tank, I would plan ahead and set up a freshwater quarantine tank, and while the fish was in quarantine, I would raise the salinity on an accelerated pace. If I didn't have room or time for a quarantine tank, I would bite the bullet and trust that estuarine fishes can handle wide fluctuations in salinity, especially when young. Does anyone have any other way to introduce brackish fish kept in freshwater to an established brackish tank?