Freshwater Fish Disease Symptoms and Treatment

Updated May 13, 2020
Author: Mike - FishLore Admin
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This freshwater fish disease page provides the common name, symptoms and treatment options for your sick fish. Before you use any medication make sure that you have properly diagnosed the fish disease and try to figure out why your fish have the disease in the first place. Many diseases are brought on by the fish being stressed due to transport, improper acclimation (e.g. not acclimated slowly) or water quality issues. If you've just set up your tank, please read about new tank syndrome which is also known as the Aquarium Nitrogen Cycle.

It's a very good idea to have a small quarantine tank for new fish so that you may monitor the fish for a few weeks before adding the fish to your main tank. You can also use the quarantine tank for your fish that come down with a freshwater fish disease and can avoid adding chemicals to your main tank. Always practice good fish acclimation techniques and don't rush things.

Try to determine the underlying problem before medicating. Many times there are water quality issues that need to be fixed first. Get and use an aquarium test kit, do frequent small partial water changes and take the appropriate measures to correct the water in your aquarium before medicating. Great water quality and good nutritious foods go a long way in keeping your fish healthy.

Whenever you use any type of medication on your tropical fish, first remove any carbon in your filtration system. If left in, the carbon will remove the medication from the water, doing you no good. Read the directions on the medication bottle very carefully!

To sum up, first determine the cause of the freshwater fish disease, fix any obvious problem(s) (water quality problems and tank mates), figure out which disease your fish has by closely observing the symptoms and then treat only if necessary.

Ammonia Poisoning or Ammonia Burn

Symptoms:
Red or inflamed gills. Fish are gasping for air at the surface. New tank setup or a tank with too many fish.
Ammonia Burn

Photo Credit: danialhimawan

Treatment:
Ammonia poisoning is easily preventable and very easily testable using an Ammonia Test Kit. Avoid adding expensive and less hardy tropical fish until the aquarium has cycled. For more information on cycling your aquarium please read about the aquarium nitrogen cycle. You can use an item called zeolite to help absorb ammonia but the best solution is to ensure that your aquarium has cycled and that your tank is not overcrowded. If your tank has not yet completed the nitrogen cycle, you will need to perform frequent Water changes to keep the ammonia levels down. Elevated levels of ammonia is lethal to fish.

Useful products to help with ammonia poisoning:
Seachem Prime
Zeolite

Camallanus Worms

Symptoms:
Red or pink worm protruding from the anus. Fish may become listless and bloated. Fish refuse to eat. This is a parasite in the intestines.
camallanus worms freshwater fish disease

Photo Credit: bizaliz3

Treatment:
Read the following thread for detailed information on how to deal with this: How To Get Rid Of Camallanus / nematode Worms

Use the following medications for camallanus worms:
Prazipro

Dropsy or Malawi Bloat

Symptoms:
Bloated fish, scales are raised, possible loss or lessening of body coloration.
dropsy

Photo Credit: fisharegreat8962

Treatment:
This is not really a disease, but a symptom of a bacterial infection and possibly malnutrition. There are medications available but try to increase the quality of the water by performing a 25% water change every other day and increase the quality of fish food given. If your fish's condition doesn't improve, try the medication. Your local pet store should have medication for this disease. Remove any activated carbon filtration before using medication because the carbon will remove the medication from the water. Also read this for more info on dropsy: Dropsy Treatment

Use the following for treating dropsy:
Kanaplex

Ich, Ick or White Spot (Ichthyophtirius)

Symptoms:
Small white spots showing up mainly on the fins but also on the body. It looks like your tropical fish has salt all over it. More information on Ich
Ich Fish Disease

Photo Credit: adncarter

Treatment:
This is a fairly common fish disease and your local pet store should have medication you can use. Here is one popular Ich medicine. Ich usually arises due to poor water quality. You can increase the temperature of your water to 82 degrees Fahrenheit to speed up the cycle time of this parasite that has three life stages. Remove any carbon filtration before using medication because the carbon will absorb the medication. Easily preventable by using a quarantine tank for a few weeks before introducing new arrivals into your main tank. For detailed directions on how to deal with Ich, read the following thread: ICH (ICK) Life Cycle and Natural Treatment
An article on Ich written by Sabi: Ichthyophthirius

To treat ich:
Super Ick Cure

Fin Rot

Symptoms:
Rotting fins, loss of appetite and laying on the bottom of the tank. This is due to a bacteria that infects the fins of the fish. It is sometimes brought about by bullying from other fish and fin nipping. Most often it is due to poor water quality.
Fin Rot

Photo Credit: pfowler5

Treatment:
There are medications available such as Tetracycline from Mardel Labs. Remove any carbon filtration before using medication because the carbon will absorb the medication. Before using medication though try increasing the quality of the foods you are feeding your fish, separate them from any fin nippers and step up your water change schedule. More information on Fish Fin Rot

Aquarium products to treat fin rot:
General Cure

Fish Fungus

Symptoms:
Cotton like growths on the body that may appear white or gray in color.

Photo Credit: anike13

Treatment:
Be sure to give your fish the best water you can by performing frequent water changes. If your fish gets a disease they may develop secondary fungus infections. Medications such as API's Fungus Cure will treat fungus problems. More information on Fish Fungus

To treat fish fungus:
Fungus Cure

Hole in the Head - HITH, sometimes referred to as Head and Lateral Line Erosion - HLLE

Symptoms:
Small holes or indentations on the head of fish, advanced cases may show markings along the lateral line of the fish. They may stop eating.
HITH - Hole In The Head

Photo Credit: miad

Treatment:
There are many theories out there, but no conclusive scientific evidence as to what exactly causes this disease. However, it may be attributed to poor water quality, lack of proper nutrition and/or the use of activated carbon for prolonged periods. However, there have been no scientific studies about the effects of the prolonged use activate carbon causing hole in the head, it's just speculation. Be sure to give your fish the best water that you can by performing frequent water changes. Give them vitamin enriched foods and change out or stop using activated carbon. Check out this food specifically made for this: NLS Hex Shield Fish Food.

Products to treat or prevent HITH:
Hex Shield

Nitrite/Nitrate Poisoning

Symptoms:
Tropical fish are lethargic or resting just below the water surface and you are getting high readings on your nitrite and nitrates test kits.

Treatment:
Nitrite / Nitrate poisoning is not a disease but will kill your fish if not remedied. Elevated nitrite levels is more harmful than elevated nitrates. It results from having a large bio-load on the filtration system or from not performing enough water changes. Perform a partial water change immediately and monitor the nitrite and nitrate levels closely until the situation is resolved. You may have too many fish in the tank and will need to perform more frequent water changes. Nitrite readings on your aquarium water test kit would indicate that your tank is still in the aquarium nitrogen cycle nitrite phase, or it is undergoing a mini-cycle if you've recently added more fish to the tank.

Do partial water changes to help lower nitrites or nitrates:
Python Water Changer

Oxygen Starvation

Symptoms:
Most or all of the fish are usually found at the water surface. They may be gulping at the surface with their mouths.

Treatment:
Check the temperature of the water. Higher water temperatures require higher levels of oxygen. You will need to increase the aeration in the tank with air stones and/or power heads and increase the flow rate with your filters. Try to decrease the temperature of the water by floating ice cubes in plastic baggies and turning off the tank light. If sun light is entering the tank from a nearby window, try closing the shades. Also, if you have an overcrowded aquarium you will definitely need to increase the aeration in your tank.

To increase oxygen in the tank:
Powerheads

Pop-Eye

Symptoms:
One or both eyes appear to be, protruding abnormally.
Pop Eye

Treatment:
This is usually the result of a bacterial infection. Try to give your fish the best water possible by performing frequent water changes. To treat this problem you can use a treatment such as Tetracycline from Mardel Labs. If possible, increase the quality of food given. Supplement with vitamin enriched foods. More information on Fish Pop-Eye

To treat fish pop-eye:
Melafix

Swim Bladder Disease

Symptoms:
Fish have a difficult time staying upright and may hang in the water. Goldfish are especially prone to problems with the swim bladder.

Treatment:
Some hobbyists feed their fish peas to treat this infection. Perhaps this works by helping in the digestion process. Try this: stop feeding the fish for a few days, give the fish optimal water conditions by performing frequent small water changes (10% every week) and see if the problem clears up.

Velvet Fish Disease (Oodinium)

Symptoms:
Velvet looks a lot like ich but velvet shows up as smaller yellow or gray dusty spots on the fish. Tropical fish with velvet will have rapid gill movement and may be rubbing on surfaces in the tank.

Treatment:
There are a lot of products out there to treat this common tropical fish parasite. For example, Aquarisol works on ich and velvet. This is easily preventable by using a quarantine tank before introducing new arrivals into your main tank.

To treat/prevent velvet:
Ick Shield