The pearly or yellow-headed jawfish Opistognathus aurifrons is prone to jumping through gaps in the
aquarium top when startled, especially in an unfamiliar tank in which it has yet to build its burrow.
I’d like to put a pearly jawfish
in my 55-gallon reef tank, but
I have a question about my tank cover. My
dealer told me that jawfish can easily jump
through small openings in the cover. For the
most part, my tank is covered completely,
but there are some small openings to allow
for various hoses and cords. How do I go
about sealing off these small gaps so my
jawfish won’t escape?
Your dealer is absolutely right
that the pearly jawfish (a.k.a.
the yellow-headed jawfish)
Opistognathus aurifrons is
one of the true aquatic Houdinis; it can launch
itself through very small openings when
startled. The same applies to other jawfish
species as well. This happens most commonly
right after the specimen has been introduced
to a new tank and before it has had a chance
to construct its burrow—so you must be extra
vigilant on the first night, especially right at
“lights out.” Suddenly plunging this fish into
darkness in unfamiliar surroundings with no
safe burrow nearby will really push its flight
response into overdrive. One technique that
works well to temporarily seal off small gaps
in the cover is to tape a sheet of plastic wrap
or window screening over the opening. You
can also stuff an inert material such as filter
floss into the gaps.
If your reef lighting includes a combination
of actinic and daylight lamps, you might
also consider putting the lamps on timers
and setting them so the actinic lamps stay on
about an hour later than the daylight lamps.
This will create a more natural dusk period
so the fish has time to adjust to the darkness
gradually, and it will be less likely to get
spooked and jump.
Once your jawfish has had an opportunity
to settle in and construct its burrow, jumping
from the tank should be less of a concern as it
should retreat to its burrow when frightened,
rather than rocket toward the surface.