Both these Acropora spp in the author’s reef tank show healthy polypextension. Healthy polyp extension is a good indication that delicate specieslike Acropora are doing well.
Recently, a situation developed in my reef tank that reminded me of my ownwords spoken to aquarists a number of times in the past. Many times in thepast I suggested that careful observation of his/her aquatic guests isextremely important; in fact, when it comes to their well being it is perhapsthe most important skill to acquire. Testing water quality with test kits isimportant, but is secondary to observation. This of course recognizes thatthere is a vast difference between the observational skills of an experiencedaquarist compared to those of a beginner. The experienced aquarist knows whatto look for, the beginner doesn’t. How early we are able to recognize adeteriorating situation is critical in a reef tank, because many of thesessile 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 offof some of my more delicate Acropora spp was a clear red alert signal, but hadI been looking more closely over the preceding months I would have recognizedyellow alert signals. Months before I noticed, but didn’t respond, to the factthat some of my old clams were not opening fully, and that my 15-year incaptivity _E. ancora _was not extending its polyps as it did in the past. Ieven noticed that some of my SPS corals were closed, not extending theirpolyps at all. However, the fish were fine and most of the corals seemedhappy. I tested for nitrates, orthophosphates, alkalinity, calcium, and a lotof other things, but everything appeared within normal reef tank waterparameters. And, it was time to do my 20% water change, so I mixed up almost200-gallons of new seawater and made the change.
Within two days of the water change RTN made its appearance. So, thinkingsomething was wrong with the new seawater I tested it for impurities, butfound nothing. Finally, I had a revelation, and tested the one thing I hadignored for many months – salinity. Both devices I had gave me a specificgravity reading of 1.032. It is my custom to change 20% of the seawater in mysystem every other month, and due to an error in the way I was changingseawater the specific gravity of my system’s seawater was rising, andstressing the animals most sensitive to high salinity. It is very important torecognize that different animals have differing thresholds in theirresponsiveness to changing environmental conditions.
It took the removal of almost 80-gallons of saltwater with its replacementwith purified freshwater to bring the specific gravity to 1.025. Iaccomplished this transition over the course of one week, and much to mysurprise and delight my corals began to recover very rapidly. Sometimes, theanswer to a problem is right in front of your nose.
We are very pleased to announce two new columns this month. One of the newcolumns, Breeder’s Net, written by Frank Marini, will present much of thecurrent, hands on information on the captive breeding of ornamental marinefish. We all understand that captive breeding will ultimately lessen thenegative impact from the collection of wild ornamental fish. With this issue,we also begin a vertebrate column. Greg Schiemer and Scott Michael will taketurns presenting us with information about the fish that we keep in captivity.Check it out!