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Cryptobia by John Nicholson

The following article is based on my personal experience and a pathology report from Patricia W. Varner, DVM, PhD AFS/FHS – Certified Fish Pathologist.

This is a sordid tale involving love, murder and betrayal. The evil arises from a villain named Cryptobia. It is an evil that is often misdiagnosed. He hides in darkness while his deeds are often blamed on others…

It all started when I decided to add some new breeding stock to my discus hatchery. I brought in 13 adults/young adults. I quarantined them in a 75-gallon tank filled with aged tap water at 84 degrees and 2 cycled sponge filters. I added 2 tablespoons of salt per 10 gallons as a precaution. I added in three 2.5 to 3 inch juveniles from my own stock that had never been exposed to the outside world. The fish were fed my homemade beef heart mixture and received a 50% water change daily. After 8 weeks everything look perfect. None of the fish had showed any sign of illness. I had a pair form in this tank. During this initial bonding/spawning cycle the rest of the fish in the tank were continually harassed and run to one end of the tank. During this a couple of the fish started showing signs of Hex. I figured it was due to the stress and did not worry much about it. I moved the pair to a breeding tank and the “hex” fish to a treatment tank.

I raised the temp in the treatment tank to 90 degrees with a single sponge filter. I treated with 400 mg of metro per 10 gallons of water a total of four times. After the initial treatment I waited 8 hours, changes 50% of the water and added the second dose. The third does was added 24 hours after the second and the forth was added 24 hours after the third. After treatment the fish started eating normally again and everything seemed corrected, but after a couple of weeks they were showing signs again. I treated them again which lead to a temporary remission of the symptoms. As a discus breeder I don’t always get as attached to the fish as others might and I was ready to get rid of this “hex” problem so I treated the fish with a double dose of metro and carried the treatment out for a full week. The fish looked like death for a couple of weeks and then started eating with a vengeance. All of the earlier signs of illness (stringy feces, shyness, grouping together, and hanging in the corners of the tank) were gone. Over just a couple of days the fish rebounded to perfect heath. Life was great except that the hex had seemed to creep into several other tanks.

While this was happening the pair that I had earlier moved into the breeding tank raised a clutch of 154 fry. I separated the fry 3 weeks after they went free swimming. I had picked up some of these fish for the purpose of crossing them into a red turquoise line of my own so I decided to pull out this male and swap him with a suspected male from a 75 gallon tank with 10 eighteen month old red turquoise fish of my own and a red snakeskin female from one of my pairs. I needed a place to put this original male so of course I tossed him in the 75-gallon tank the new male had been pulled from.

I mix fish around in my tanks all of the time. When I do this I will often see some aggression but it will be short lived. This time the aggression was fairly excessive but I had no doubt that it would subside before I returned from work. When I got home that evening I discovered that I had been sadly mistaken about the aggression subsiding. The new male was not only dead but his eyes were missing. I have never seen discus do this before. I removed the dead male and also decided to move the female snakeskin back in with her mate. In less then a week all of the remaining fish in the 75-gallon tank were very ill. The female snakeskin and here mate were also both very ill. I tried several treatments including furan2, tetracycline, erythromycin, and salt. One day they might look a little better and then next they would look worse. This pattern continued as they slowly lost ground. The reoccurring hex problem also continued in my other tanks. It was at this time that I decided to send in 3 specimens to Dr. Varner.

This was one of my better decisions in a long time. 2 of the specimens were “healthy” fish from a couple of different tanks (both of which had had bouts of reoccurring hex) and the only remaining live fish from the 75 gallon tank (I had also lost the snakeskin pair) By this time the sick individual was suffering from a host of what Dr. Varner called “secondary opportunistic aquatic bacterial pathogens”. I have a hunch that many of the fish that die from cryptobiosis are mistakenly determined to have died from one of the many secondary infections that Cryptobia hides behind. I was very lucky that Dr. Varner had noticed some “lightly encapsulated granulomas with amorphous necrotic center” and also “lymphocytes, histocytes, melanomacrophages, and rare multinucleated giant cells”. Instead of just letting it go she spend the next couple of weeks doing all kind of tests. She also discovered these granulomas in the spleen, liver, caudal kidney, and heart. The brains were unaffected. It is very hard to diagnosis chronic cryptobiosis but Dr. Varner was reasonably certain that it was the root cause of problem.

The fact that the two “healthy” fish had the same abnormalities was what clued me into what I had been seeing in my tanks. It was not reoccurring hex that I had been chasing but Cryptobia. This parasite was slowly weakening the fish. In the beginning there was normally no signs but if the fish gets stressed they can show the normal signs of hex (stringy feces and loss of appetite). If somehow caught at this stage it can be treated successfully with metro. Since at this stage I was still uneducated in this disease I do not know the exact dosage. To get rid of it I treated in what I call a “strong and long” formation. Do so at you own risk. Once the problem has been around for a while metro will not cure the problem. I used a product called dimetridazole (trade name Emtryl or Unizole). 100grams of product will treat 330 gallons of water. You will need to treat for 3 concessive days. This means that 100 grams is enough to fully treat (3 days) 110 gallons of water. The containers that I received came with a plastic scoop. I determined that there were exactly 33 scoops in 100 grams. This made the dosage easy. I used one scoop per 10 gallons of water once a day for 3 days. This is not an easy product to find anymore, but I was able to find that it is still widely used in the world of racing pigeons. A search of pigeon supplies and a few phone calls should lead you to the product.

I observed some interesting developments during treatment. The tanks that I knew had been exposed all turned cloudy after the first treatment. They clouded to the point that I could not see a breeding pair in a 29-gallon tank. I had to add some extra aeration but otherwise the fish were unstressed and started eating better after the first treatment. Some tanks that I felt were “clean” stayed crystal clear. The tanks had the same water parameters and dosage level. I do not know exactly what that means but thought it was worthy of noting. I also notice that if you get interrupted while medicating the tanks and accidentally double treat a tank you will have a death rate of approximately 70%. To make matters worse this was one of the “clean” tanks that I was just treating for my own piece of mind. These were the only deaths that I experienced during treatment. At the time the smallest fry that I treated were about one inch. The only tank I had not treated was a pair with eggs. Based on the success of the other tanks I have now started treatment on this pair. The fry are only 10 days old but after the initial treatment they are not showing any signs of stress.

In conclusion I feel that many people, just like myself, have been treating the symptoms but not the root problem of the “reoccurring hex” illness. Without stress your fish can live with Cryptobia for many months without any symptoms. With proper care these fish are able to spawn and raise fry with just a slight reduction in success rates. When the fish do breakdown we often blame the secondary conditions for the deaths that we see. Even if you send in a fish for a pathology report it can easily be missed. The good news is it appears to be completely curable with the right medication and the treatment appears to be easy on the fish. I hope that the exposure of this menace can lead more people to successful discus keeping.