the main reason for acclimation (FYI)


Staff member
RC Mod
....salt. Salinity. Salt balance in the critter's tissues.
More than anything else, more than temperature change, more than any difference of trace elements in the water---salt level is critical. Lethal, if mismanaged.


Our cells, a fish's cells, a coral's cells---all have the ability to intake and shed moisture. If the salinity on one side of the cell membrane is higher or lower---this is bad news and can result in dehydration or even the rupture of cell membranes. You'll hear the term "osmotic shock." That's this process. It's lethal and painful. It ruins kidneys, in particular, which is why things may survive for 3 days and then die mysteriously. Kidney failure doesn't kill immediately: toxins build up in the bloodstream and the kidneys can no longer function. In lower level creatures which have no kidneys, the damage is more generalized: general tissue disruption.

So what does acclimation do?

It provides time and intermediate stages for the critter's tissues to push out or take in salt. Time for an adaptive biologic process, in other words. This means it equalizes salt/water on both sides of the membrane of its cells.

Could you skip acclimation and just put the fish/critter into your water if it exactly matched the salinity of the water the critter is in?
In a word, yes, it would be fine to do that. You should consider temperature. But salinity is the main deal. A refractometer, which gives readings accurately to .001 of salinity is a very, very good investment if you are doing this.
I recommend adjusting your quarantine tank exactly to the salinity of your lfs. That way you can just take a new fish from your bag and into the qt tank immediately, and adjust the qt tank salinity over a period of days by topping off with fresh or salt water, as indicated. This is the gentlest method of acclimation, and of course, you get a chance to be sure your new fish is not bringing a parasite into your tank.