Tropical fish are beautiful. You have your fish; you have your tank set up just like you want it and enjoy spending time relaxing while watching and enjoying your tank. Then you see it. One of your fish has a large lump – relaxation time is over. Tumors in tropical fish are more common than you might suspect and a lump on one of your fish is the first sign of a tumor.

Just like any living being, this disease can occur in your fish and to you is upsetting. You enjoy your fish and have become attached during the process of selecting your fish, setting up your tank and the daily care and feeding. So what can you do when you suspect a tumor in one of your fish? Let’s look at the causes, symptoms, and treatments of the two most common tumors in tropical fish.

There are two common types of tumors that your fish can get. The first is Lymphocystis which is also known as “Cauliflower Disease” because of the appearance of the growth. This type of tumor is caused by a viral infection and causes the cells in your fish to become megaloblastic and form small tumors. These tumors can usually be seen along the lateral line or the pedicle where the fin meets the body.

Symptoms of Lymphocystis are lethargy and you will begin to notice that your tropical fish has trouble swimming due to loss of balance. As the tumor in your fish grows,  he will also begin to lose control of his swimming depending on the location of the tumor. Lymphocystis can possibly respond to treatment. To treat the tumor in your tropical fish change the water frequently to reduce the amount of ammonia and nitrites. This will reduce stress on your fish and will help the fish fight the infection and possibly shrink the tumor.

The second type of tumor that your tropical fish may have is a solid tumor. These are tumors that can be either benign or malignant and can also be very slow or fast growing. Solid tumors can show up on any part of your fish externally or internally. These tumors are not usually noticeable until they have become large and have begun to affect the fish. Some ways in which your fish will be affected are obscured vision, if the tumor is on or near its head; changes in feeding habits, usually when the tumor is internal, and swimming, when the tumor is either internal or external.

Unfortunately, with the exception of frequent cleaning of your tank water, tumors in tropical fish are untreatable. Remember that all tumors aren’t cancerous, so unless the tumor is affecting the quality of life for your fish, there is no need for concern. However, if the tumor grows to the point that your fish can no longer eat or swim properly and is suffering, you need to consider euthanasia to prevent suffering. As difficult as this may be, when you detect a tumor in your tropical fish, this may be your only choice.

This disease is a common bacterial infection that is also known as Columnaris and can occur from overcrowding and low oxygen levels in the tank or being brought in when a new fish is introduced into your aquarium. The bacteria enter the fish through their mouth and gills, or through any small wounds that the fish may have.

Symptoms

The symptoms of Cotton Mouth disease are first seen in frayed and ragged fins shortly followed within 24 to 48 hours by mold-like lesions or sores. The sores can be obvious as with a ‘saddleback’ lesion, which extends from the dorsal fin down each side on the fish like a saddle, or they can appear to be only a ‘paler’ area or not as shiny as the rest of the fish. After these first signs, the mouth will become eaten away and the gills will change color to either a light or dark brown. As signs of gill damage set in, the fish will begin to breath rapidly and laboriously. Within 48 to 72 hours after these signs appear, the fish can die.

Treatment

If you have diagnosed your fish as having Cotton Mouth disease, you need to begin immediate treatment. Your first step is to isolate the sick fish from the healthy fish and give it medicated fish food that contains oxytetracycline, an antibiotic. If the fish isn’t eating, you will need to apply a topical antibiotic such as TMP Sulfa, Sulfa 4 TMP, or Triple Sulfa made for this disease.

Next, change the water in the tank and vacuum the gravel. Add aquarium salt to improve gill function and discontinue carbon filtration during the treatment. Increase aeration and water agitation to dissolve oxygen levels. This will help the fish that are having trouble breathing due to gill damage.

It is important to recognize the symptoms of Cotton Mouth disease in your fish because it is highly contagious. Because this disease spreads rapidly, it has the potential to infect every fish in the tank, and destroy all of your fish. Keep your tank well aerated, clean, and don’t overcrowd it. These precautions will help prevent this fatal disease.