Both these Acropora spp in the author’s reef tank show healthy polyp
extension. Healthy polyp extension is a good indication that delicate species
like Acropora are doing well.
Recently, a situation developed in my reef tank that reminded me of my own
words spoken to aquarists a number of times in the past. Many times in the
past I suggested that careful observation of his/her aquatic guests is
extremely important; in fact, when it comes to their well being it is perhaps
the most important skill to acquire. Testing water quality with test kits is
important, but is secondary to observation. This of course recognizes that
there is a vast difference between the observational skills of an experienced
aquarist compared to those of a beginner. The experienced aquarist knows what
to look for, the beginner doesn’t. How early we are able to recognize a
deteriorating situation is critical in a reef tank, because many of the
sessile animals are very intolerant of certain changes to their environment.
The truth of this was brought home to me recently when an out break of RTN
(rapid tissue necrosis) began to develop in my reef tank. Tissue sloughing off
of some of my more delicate Acropora spp was a clear red alert signal, but had
I been looking more closely over the preceding months I would have recognized
yellow alert signals. Months before I noticed, but didn’t respond, to the fact
that some of my old clams were not opening fully, and that my 15-year in
captivity _E. ancora _was not extending its polyps as it did in the past. I
even noticed that some of my SPS corals were closed, not extending their
polyps at all. However, the fish were fine and most of the corals seemed
happy. I tested for nitrates, orthophosphates, alkalinity, calcium, and a lot
of other things, but everything appeared within normal reef tank water
parameters. And, it was time to do my 20% water change, so I mixed up almost
200-gallons of new seawater and made the change.
Within two days of the water change RTN made its appearance. So, thinking
something was wrong with the new seawater I tested it for impurities, but
found nothing. Finally, I had a revelation, and tested the one thing I had
ignored for many months – salinity. Both devices I had gave me a specific
gravity reading of 1.032. It is my custom to change 20% of the seawater in my
system every other month, and due to an error in the way I was changing
seawater the specific gravity of my system’s seawater was rising, and
stressing the animals most sensitive to high salinity. It is very important to
recognize that different animals have differing thresholds in their
responsiveness to changing environmental conditions.
It took the removal of almost 80-gallons of saltwater with its replacement
with purified freshwater to bring the specific gravity to 1.025. I
accomplished this transition over the course of one week, and much to my
surprise and delight my corals began to recover very rapidly. Sometimes, the
answer to a problem is right in front of your nose.
We are very pleased to announce two new columns this month. One of the new
columns, Breeder’s Net, written by Frank Marini, will present much of the
current, hands on information on the captive breeding of ornamental marine
fish. We all understand that captive breeding will ultimately lessen the
negative impact from the collection of wild ornamental fish. With this issue,
we also begin a vertebrate column. Greg Schiemer and Scott Michael will take
turns presenting us with information about the fish that we keep in captivity.
Check it out!