Toxic Water or Fright Syndrome
A Discussion of Causes, Prevention and the Emergency Treatment of Afflicted Killifish
By Ted Dalgleish (Reprinted from the Journal of the American Killifish Assoc. Volume 30, No. 4, 1997)
Toxic water or Fright Syndrome (hereafter referred to a TWS) is first manifest by an acute behavioral change from the normal in aquarium fish. The first clues to the aquarist are subtle. Fish that usually move actively about at all water levels hang listlessly just below the surface and peck apprehensively at their favorite foods, or will not eat at all. Secondly, and more noticeable, the fish move jerkily or make sudden spiral rushes in various directions when they are startled. These rushes finally end with the fish having a severe spasm in which the back is arched and gill plates and pectoral fins stand out at right angles to the body. At this point the fish will appear dead, and in fact the fish will die momentarily if the aquarist doesnt promptly intervene.
Unfortunately TWS is most likely to occur in a group of fry when they are about 1 cm - 2 cm in length and still being raised in smaller fry containers. Although virtually indispensable to killie keepers, these boxes are not totally transparent and one cannot adequately monitor the fish in them. Also, they do not contain much water; making chemical changes occur both dramatically and suddenly. Many aquarists introduce a few snails, for instance, in order to clean up uneaten food or decaying brine shrimp relaxing in their belief that any waste problems are being taken care of. Snails do help out, up to a point, but being living creatures, they too produce waste and utilize oxygen. To my way of thinking it is like adding competition to the fish in a system that is on a biological razors edge to begin with.
Prevention of TWS is relatively simple in the scenario just discussed. Carefully siphoning off uneaten food of any kind or sucking it up with a meat basting syringe and replacing the water from a suitable supply on a twice weekly (or more frequent) basis will virtually eliminate TWS in small containers. Incidentally, the fish will grow in direct proportion to the frequency of water changes.
Regarding the cause of TWS, there have been a lot of articles written about the importance of monitoring aquarium water for chlorine, ammonia and nitrate levels. Chlorine is one of the most overrated threats to life in the aquarium. It is an irritant gas and is readily detectable to humans in concentrations that are far below the threshold which is injurious to fish life. Regarding ammonia and nitrite (a salt of nitrous acid), a buildup of either is a harbinger of things to come. But would it surprise you to know that, in the majority of TWS cases, there is a buildup of neither nitrate nor ammonia detectable in water taken from the aquarium?
What then are we dealing with and how do we know that we are getting close to the edge? Look to the most simple, and probably the cheapest test of all. Get out your old pH test kit! You will find that regardless of your initial water supply, the pH has become dramatically more acidic. This means that your water is already soft and acid as recommended in most aquarium literature for the majority of Killifish.
The emergency response to TWS is to remove all of the fish...those stricken, those appearing to be normal, and those appearing to be dead. Place them into a small aquarium with water from a healthy tank. To this add 1/10th of seawater with a specific gravity of 1.025 (or whatever you use to hatch brine shrimp). Marine mix seems to be better than aquarium, kosher or pickling salt, but any of these will work as an alternative. Place an air release, either a fine air stone or slowly bubbling airline, into the tank and cover the whole works with a dark towel. In less than an hour, a careful peek will reveal that many of those that were nearly gone, and some of the dead ones are back to an even keel. Do not disturb them for a few more hours. Introduce the survivors to a larger quarters after acclimating them to their new water supply.