Nora and Jen ask Dr. Jessie Sanders, a fish veterinarian with extensive experience working with betta fish tumors, to share her insights into white bumps, patches, or growths in bettas, including treatment options and practical tips for betta keepers managing this condition.
Jen: Nora, I’d like us to tackle an unfortunate and common issue that comes up on the betta groups I frequent. So many betta keepers have beautiful bettas with great aquarium set-ups, a varied diet—everything a betta needs. And yet, their bettas get these white growths, bumps, or patches, and no one is sure exactly what they are or what, if anything, can be done. Do you have any insight into this?
Nora: You have come across one of the most common problems that betta keepers call fish veterinarians about. I am going to “phone a friend” and ask Dr. Jessie Sanders, the veterinarian who owns Aquatic Veterinary Services in California to share her knowledge and experience working with betta fish that have this type of problem. Jessie, what are the most common causes of white patches or growths in the betta fish that you see in your practice?
Jessie: It’s great to join you both today! Our office gets a lot of calls about concerning lumps on bettas. Although it’s always best to have an in-person appointment, here’s what we know about this presentation in bettas. Larger white patches in betta fish are very commonly chromatophoromas or pigment cell tumors. We frequently see iridophoromas in bettas, which are specifically tumors of the iridescent scale pigment. These can be seen as larger than eyeball-size raised white growths that can occur anywhere on a betta fish’s body. They are typically very benign growths that the betta will not even notice. If they are large enough to be felt when swimming, they can be gently debrided with a Q-tip as the fish swims by. This will cause a chalk-like plume that is not toxic to the fish, water or other inhabitants.
Nora: I touched on the topic of chromatophoromas briefly in an article I wrote explaining the cause of “Diamond Eye” in bettas, but I didn’t come across any mention of how easily these tumors could be removed from the fish. Human physicians and veterinarians commonly use debridement to remove dead tissue from wounds, but who knew that fish veterinarians were using this to treat chromatophoromas in betta fish!
Jen: Although it can be concerning to see a growth like this on your betta, it is also fascinating in a way that they seem to have so many issues associated with their pigment cells, like the scales growing over their eyes, or these other pigment cell tumors. It’s interesting to ponder if it could be related to all the line-breeding these domestic Betta splendens have gone through to achieve all the incredible colors and varieties available these days.
While I haven’t had a betta fish with a tumor so far, I have experienced a koi halfmoon plakat with a strange growth under his chin, sort of protruding from the operculum. I’ve also seen other people in the forums asking about this specific kind of growth.
Nora: It’s amazing how many causes there are for lumps and bumps on fish besides cancerous tumors. The growth you are describing coming out of the gill of Mr. Fish (may he rest in peace) sounds a lot like a goiter.
Jessie: Goiters in bony fishes, such as bettas, goldfish and koi, typically show up as a swelling behind the operculums, not usually under their mouths as is seen in other species, including sharks. This will appear as a flesh-colored protuberance coming out from the gill slit. These can only occur directly behind the gills and are commonly caused by malnutrition.
Nora: Another problem I have commonly seen in betta fish is swelling in the area of the coelom (belly). Sometimes this is from a growth around or inside of the coelom, and other times it seems to be that the entire belly is distended.
Jessie: A protruding belly on a betta is typically indigestion caused by inappropriate feeding or water temperature. It can also be caused by a kidney infection or internal tumor. If you want to know the exact cause of a protruding belly, you need to take your fish to a veterinarian. Chromatophoromas are another cause of protruding bellies in betta fish, as they are external masses that can develop in that area since they derive from pigment cells within the epithelial layers of the skin.
Jen: What are some common signs that a betta has a chromatophore tumor? Does anyone know yet why they seem so prone to this, and what causes it?
Nora: The most common sign of a chromatophoroma is an external mass on the fish’s body–it can be on the eye, head, body, or fins. It may be different colors depending on the type of pigment cells the tumor started from. Whereas white spots from external parasites tend to be small and spread all over the fish, it would be more likely for a chromatophoroma to be located in one spot and the size of the fish’s eye or larger.
Jessie: Like other types of neoplasia (cancer), these growths can occur due to genetics, environmental issues, or bad luck. We do not know at this time why they are more common in bettas than other fishes.
Jen: What do betta keepers need to know about managing a tumor in their fish? Is there anything practical that can be done?
Jessie: If your fish has normal behavior and appetite, these growths are fairly self-limiting and will not harm them or affect their longevity. If the lump is causing them to have increased periods of rest (what is longer than normal for a betta, who knows?) or decreased appetite, the mass can be gently debrided with a Q-tip as they swim along.
Jen: If a client brings you a fish that you think has a chromatophore tumor, what happens to the fish at your clinic?
Jessie: As with all fish appointments at Aquatic Veterinary Services, an evaluation of their environment, including water quality testing and a dietary assessment will be performed prior to a physical exam. Betta fish can be tricky to sedate properly, given their specialized labyrinth organ, so your fish may or may not have a full physical exam. These can also be difficult given the fish’s very small size. Chromatophoromas can be easily diagnosed with a swab and/or microscope evaluation.
For larger fish, cryotherapy or CO2 laser can be utilized to treat deeper tissue layers of chromatophoromas. However, given a betta fish’s small size, these treatments are not of great benefit. If a chromatophroma is on a tail fin, the fin can be trimmed to remove the mass; however, chromatophoromas on the fins are typically more problematic for the betta since they will greatly hinder balance and swimming. As long as the fish is acting and eating normally, typically we leave the lumps as they are. If we determine that something other than a chromatophoroma is causing the lump on the betta fish, we need to pursue a different course of treatment. The only sure way to diagnose for certain a chromatophoroma is a visit from your fish veterinarian.
Jen: Thanks so much for all this great insight, Jessie! I think betta keepers who have a fish with a tumor will find this comforting, actually. What I see on the groups and forums I follow is that these devoted betta keepers are really concerned with their betta’s well-being and happiness most of all. They want to treat their betta as well as they can, so it’s important to them to understand if there is any treatment they should do, or if their fish is suffering.
Jessie: Chromatophoromas do not typically affect longevity or quality of life, but this will depend on where the mass is located. If your fish’s behavior and appetite are normal, they may not require any treatment. If your fish stops eating, cannot swim to the top of their tank or lists to one side, it is time for additional intervention.
Nora: Jen and I covered the topic of euthanasia and thinking about a fish’s quality of life in a previous conversation. It was a hard topic to cover, but very important for fish owners who care deeply about making sure that their fish is not suffering.
Jessie: Even for fish with a serious disease, if they are still swimming and interested in eating, I do not typically recommend immediate euthanasia. But once a fish stops eating, isolates itself, and cannot hold its body position in the water, that is when it is time to seriously consider euthanasia.
Nora: Jessie, we are so appreciative of you lending your expertise to our conversation about bumps, growths, and tumors on betta fish. You have so much knowledge and experience about not just this, but many different diseases in fish. We may have to consult you again in a future conversation! I think this discussion will really help betta keepers who have a fish with this problem to better understand what is going on with their betta, their options for treatment, and what is important in considering and managing their betta’s quality of life.
Connect with Dr. Sanders:
Relevant Articles:
Bettas for Beginners by Jennifer O. Reynolds, M.A.
Fish Diseases: Diamond Eye in Bettas by Nora Hickey, D.V.M.
White Patch on Betta Fish: Treatment for a Pigment Cell Tumor by Jessie Sanders, D.V.M.
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