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Neon Tetra Disease

Despite the name, neon tetra disease can affect a range of other tetras besides neon tetras, and has been reported from a variety of other aquarium fish as well.

By Neale Monks, Ph.D. |

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Neon tetra disease is difficult to diagnose reliably and even more difficult to treat. Despite the name, neon tetra disease can affect a range of other tetras besides neon tetras, and has been reported from a variety of other aquarium fish as well.

At very low levels of infection there may be no symptoms visible at all, and it is usually the case that the more obvious symptoms of neon tetra disease are only apparent on heavily infected aquarium fish a few days away from death. Infected aquarium fish will often spend less time with their schoolmates than normal, typically hiding away under aquarium plants and showing no interest in fish food. The aquarium fish’s colors fade, and sometimes gray or white patches on the flanks become apparent. In advanced cases the aquarium fish may have trouble swimming, and the fish may develop odd swellings or contortions indicative of damage to the musculature. Usually the aquarium fish dies within two or three days of the first symptoms of neon tetra disease becoming apparent.

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Neon tetra disease can infect other aquarium rish as well as the tetras
Despite the name, neon tetra disease can affect a range of other tetras besides neons, and has been reported from a variety of other aquarium fish as well.

Unfortunately for the aquarist several other diseases can cause similar symptoms to neon tetra disease, including systemic bacterial infections, chronically poor diet and/or environmental conditions, and even old age. Some aquarists have coined the term “false neon tetra disease” to refer to bacterial infections with broadly similar symptoms.

The parasite responsible for neon tetra disease is called Pleistophora hyphessobryconis. It is a single-celled organism that gets into its host by being consumed alongside fish food. The parasite was first identified in neon tetras, hence the common name, but it has also been reported from a range of other tetras as well. Less frequently, it has been reported to affect non-tetras including minnows, danios, goldfish, and even angelfish.

Life Cycle
Pleistophora hyphessobryconis gets into the aquarium fish through accidental ingestion. Under aquarium conditions this is most commonly some sort of scavenging or cannibalism, the parasites inside a dead fish being consumed by a healthy fish. Once inside the gut the parasite spreads throughout the fish’s body and eventually gets into the skeletal muscles where it matures. Eventually the parasites produce large numbers of spores, and when the host fish is eaten by a predator or consumed by a scavenger after death, the spores are then able to get into new fish.

Parasites in tissues other than the muscles, for example those in the gut or kidneys, may release viable spores into the aquarium water in other ways as well, even before the host fish dies. This is why isolating infected aquarium fish is so important. In one laboratory experiment, an infected neon tetra was placed alongside a group of ten zebra danios, and no fewer than seven of those danios became infected!

There are no effective medications for neon tetra disease, and infected fish are normally removed and euthanized at once to prevent subsequent infection of healthy fish. However, because neon tetra disease can be confused with bacterial infections, some aquarist may want to place infected fish in a quarantine aquarium and treat with antibiotics. If the aquarium fish recovers, then it can be returned to the main aquarium after a suitable quarantine period.

Toltrazuril has been used experimentally to treat neon tetra disease microsporidean parasites including Pleistophora hyphessobryconis, but thus far there are no medications commercially available.

There is some evidence that healthy aquarium fish can fend off neon tetra disease infections under their own steam, and conversely, neon tetra disease seems to be most common when aquarium fish are stressed or otherwise weakened. In the case of neon tetras for example, their maintenance in hard water and at excessively high temperatures are surely reasons why so many people have problems keeping them alive for anything like their full lifespan of 4 to 5 years. While they can tolerate harder water for short periods, for long-term success they should be maintained at 2 to 10 degrees dH, pH 6 to 7.5. Water temperature should also be carefully controlled, ideally between 72 to 75 degrees F, making neon tetras particularly suitable for maintenance alongside other aquarium fish that prefer relatively cool conditions, such as pearl danios, black phantom tetras, golden dwarf barbs (Puntius gelius) and Corydoras catfish.

Because neon tetra disease is highly contagious it is very important to remove affected aquarium fish as soon as possible. Treatment of neon tetra disease with an antibiotic may be worthwhile if the fish is still mobile and feeding, but otherwise the fish should be euthanized and the body disposed of in the trash. Needless to say, neon tetras should never be purchased from aquariums with sick or ailing fish, and even when apparently healthy fish are bought, they should be quarantined for a period of 4 to 6 weeks before being placed in a community aquarium.

Some aquarists have found it difficult to keep neon tetras alive for more than a few months, often losing one or two every few weeks until their initially beautiful school of neon tetras is completely gone. One workaround here is to avoid neon tetras in favor of similar fish that aren’t affected by neon tetra disease, or if they are, less commonly. Cardinal tetras for example are mostly wild-caught and appear to be plagued less by neon tetra disease than farmed neon tetras. Cardinal tetras are a bit more expensive of course, and must be kept in warm, soft, acidic water conditions; aim for 79 to 82 degrees F, 2 to 10 degrees dH, pH 5.5 to 7.0. In harder water Celebes rainbowfish (Marosatherina ladigesi) and dwarf rainbowfish (Melanotaenia praecox) make good alternatives, and both have the luminous electric blue color that makes neon tetras so eye-catching.

Neale Monks studied zoology at the University of Aberdeen in the north of Scotland and obtained his Ph.D. at the Natural History Museum in London. He's also been a marine biologist, a high school teacher, a university professor and a museums exhibit designer. But his real love has always been tropical fish. His particular interest in brackish water fish culminated in his editing of the first encyclopaedic book on the topic, 'Brackish-Water Fishes', published by TFH in 2007. Neale regularly contributes to all the major English-language fishkeeping magazines, focusing especially on community tanks, biotopes, healthcare and water chemistry issues. After living in London and then for a while in Lincoln, Nebraska, Neale now lives in a quaint cottage in a pretty market town in Hertfordshire, England, where he divides his time between teaching and writing.

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Patsy    International

2/8/2016 9:48:59 PM

Surprisingly, my neon tetra survived! I put him in a quarantine tank and used salt and Bettafix (tea tree oil), all that I had on hand because I really didn't think he would make it because he was in horrible shape; I actually almost killed him because I thought he was suffering so badly. However I felt bad and stopped it midway. He has been in his quarantine for six weeks. His color is not fully back but he is swimming around and eating! And he looks alot healthier. His spine is slightly kinked, much better than before. I am not sure what healed him, either he was a fighter, or the meds or a combination. But there is one success story!

Codi    International

1/25/2016 9:15:13 PM

I bought a fish tank not long ago and bought 3 neon tetras exactly 8 days ago, they swam together and where very active and all had a very vibrant stripe. But I have just gone to give them there night feed now and only one even tried to get food which I thought was odd, and he has been swimming away from his school the last 2 days, he's the only active swimmer left and has the brightest stripe, the rest kinda sit near the back of the tank and don't move to much and look a little gray, should I try and remover them or wait it out? Any help would be great, thanks!

anns    International

12/12/2015 4:06:07 PM

Everywhere I go everyone says "No known cure just kill your fish and start over"
Honestly is there NO respect for a life trying to fight illness among fish keepers anymore? It's like it's the pet shop industry writing these reports with the flippant way their written. I don't just mean this post its all over the internet the whole "just kill your fish and buy new ones and maybe a new tank to while you are at."

Truth is the main problem to the "no known cure" is because very very few fish keepers even bother to report any successes or even NTD outbreaks let alone go see a vet about their fish! (yes there really are Vets that Do help fish.) IF all of us fish keepers around the world band together and start going to our vets and reporting in about this nasty illnesses that afflicts our little fishy friends the more chance there is of the Boffs in the vet uni's of finding and getting well working cures out there for them.
Sadly I've got 5 goldfish at the moment All suffering with NTD because someone thinking it would be a nice thing for me to find in my tank when I got hope added some tetra's to the tank (all died or eaten apparently), my living room now has 5 tanks in it, each fish in its own hospital tank due to differing levels of infection. One poor girl now 20 years old has even changed colour with it, (she's not looking good but she is hanging in there at the moment) I'm having some luck with treating this out brake with the table seasoning course sea salt of all things as well as NT labs Anti-Ulcer & and finrot for the lesser infected (to start) followed up with anti fungal treatments and lastly anti parasite treatments, followed in with king British disease clear to help them heal. The big problem is you are not going to be just fighting NTD but a heck of a lot of secondary infections that take advantage of the weekend state of your fish. So it's not really known if NTD is what kills your fish at this stage due to everything else that hits them at the same time. So when you are treating NTD is like laying siege to a castle, both you and your fishy friends are in for a very long battle, and most of that is up to how stubborn your fishy friends are, some may not be strong enough and sadly the kindest thing would be to euthanize them and give the bodies to your vets to send off for study as this will also aid in finding a cure. However if you have stubborn fish try helping them fist, and remember talk to your vets the more is known about NTD the better chance there is of getting a cure for this nasty fish killing parasitical fungus that invites its evil little fish killing friends to the party.

tomomomo    new york city, NY

4/3/2014 5:52:23 PM

thank you the info will be helpful
but i also wish there was a cure.

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