When we consider the term “acclimation” as it relates to marine aquarium fish, we usually think of the relatively brief period during which—with the hobbyist’s help—they gradually adjust to the temperature, pH, and other water parameters in a new system. But in actuality, it takes several days to weeks after introduction for a fish to become fully acclimated to the conditions and other livestock in a new aquarium environment.
It’s during this period that certain health and compatibility problems are most likely to arise, so hobbyists must be especially vigilant and take precautions to ensure their new aquatic charges adjust to their new digs successfully. Here are a few issues to watch for in those first crucial weeks:
#1 The fatal leap
Frightened fish have the potential to leap from an uncovered tank to their death at any time, but never are they more skittish and prone to jumping than during the first few days in a new tank—especially after lights out on that first night. Stands to reason, doesn’t it? After all, how would you feel if you were shoved unceremoniously into a room full of strangers, some of whom appear to resent your arrival, and before you could even get your bearings, someone suddenly shut off all the lights? You’d probably be pretty jumpy, too!
Keeping the tank well covered is the most obvious solution to this problem, but it’s also helpful to arrange the rockwork so there are plenty of hiding places not already claimed by established residents, minimize human activity outside the tank, and provide a gradual change in the lighting scheme from daylight to dusk to dark. I also sometimes leave a room light on during this period so the new fish isn’t plunged into complete darkness when the tank lights turn off.
#2 The hunger strike
Thought you got over this during quarantine didn’t you? Unfortunately, it’s not uncommon for a fish that was feeding at the LFS and in quarantine to go off its feed when introduced to a display aquarium with new tankmates. Usually, this hunger-strike behavior is temporary and the fish comes around once it gets comfortable in its new home, but I have had fish refuse food for as long as several weeks.
If this behavior persists, be ready to target feed the hunger-striking specimen or to entice it with something much harder to resist (e.g., chopped clams/clam on the half shell, live mysids, live ghost shrimp, etc.).
#3 Tankmate hazing
Compatibility issues are most likely to arise immediately or shortly after a new fish is introduced (which isn’t to say they can’t materialize later)—whether it’s a case of the newcomer being bullied by an established specimen or vice versa. Sometimes the aggression is short-lived and sorts itself out, but other times it becomes necessary to remove one specimen or the other (either the aggressor or the aggressee) to prevent injury or death.
It’s vital to keep a very close eye on all specimens during a new fish’s acclimation period and to be prepared to take prompt action if serious, persistent aggression is noted.
#4 Succumbing to stress
Acclimating to yet another aquarium, set of water parameters, and community of tankmates can stress a new specimen to the point that it becomes ill and ultimately succumbs. In fact, many “mysterious” fish deaths can likely be attributed to this phenomenon.
The best defense against undue stress is to provide an aquarium environment that is as therapeutic as possible, which means maintaining stable, appropriate water temperature, pH, and specific gravity; keeping dissolved pollutants to a minimum; minimizing aggressive interactions among specimens; minimizing movement and activity outside the tank; offering a variety of high-quality, appropriate foods; providing ample hiding places; etc.
What’s your #5?
As usual, I’m sure I’ve left something important off this list. So what’s your #5? Please let us know in the comment section below!
