Freshwater Fish Diseaseprateek kumar
Freshwater Fish Disease
This is on account of Nitrogen cycle being incomplete and the reasons could many, to name a few: overfeeding, overstocking of tanks, absence or inadequate functioning of filtration system etc. The symptoms are Red or inflamed gills, fish are gasping for air at the surface. This is common in new tank setup.
Fresh Water Fish Remedy
Ammonia poisoning is easily preventable. 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 a substance 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 to keep the ammonia levels down.
Red or pink worm protruding from the anus, resulting Fish may become listless and bloated and refuse to eat.
Remedy : Change the water in the tank to be treated to the maximum level possible However, don’t scrub the tank clean. Add medication and watch the fish for the next few days (2-3 days). Remove any dead ones. Dry the removed dead fish on a newspaper or paper towel and into the trash. Please do not flush the infected dried fish into the commode as this might led to spreading the infection to waterways / system. feed the remaining live fishes as usual. After 3 days, change the water again to remove the dead Nematodes and the Medication. Further repeat the treatment of the tank in 3 weeks to ensure that pregnant females may expel infected eggs and thereafter change the water in 3 days.
Take precaution to disinfect everything that touches the water : siphon, nets, buckets, etc. In case you find a fish with visible signs of worms in your quarantine tank, don’t move them to a tank with uninfected fish. This will result in spreading the parasite. The visible signs of worms only indicate that the other fishes have it and are in various stages of worm infestation. Treat the entire tank & sanitize everything that the water touches. This parasite can be spread in droplets of water by using the same nets, siphon, etc. from the infected tank. If you have multiple tanks it would be prudent to treat all of the tanks if you use same nets, etc.
It may be necessary to euthanize infected emaciated / bloated fish & those with visible signs of worms. As, even after the treatment, if fish does not expel all of the worms, the worms will decay inside the fish, leading to its eventual death and secondary bacterial / fungal infections. Then the secondary bacterial and fungal infections then can spread to the surviving tank–mates causing new problems.
Some recommend euthanizing all fish, sanitizing everything with bleach solution & starting over with a new cycle. If you do this it is advisable that you remove all water, fish, gravel, filter media. Leave in all decorations you want to reuse & refill tank. Treat tank, wait 3 weeks to do follow up treatment. Then sanitize everything & start over.
It is recommended that you wash any towels used while doing water changes separate from other clothes in bleach & hot water.
Dropsy or Malawi Bloat :
Bloated fish, scales are raised, possible loss or lessening of body coloration.
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 carbon filtration before using medication because the carbon will remove the medication from the water.
Dropsy is not a specific disease, but rather a symptom of a deteriorated health condition. With dropsy, the fish will have visible swelling and projected scales. This is the result of a fish not being able to regulate the amount of fluid in a part of its body. The affected area is typically the abdomen; specifically, it is most often the visceral cavity that houses a number of organs, such as the stomach, intestines, gall bladder and kidneys. The failure to regulate fluids is a symptom; therefore, there is usually some other disease involved that starts the process (caused by poor water quality, stress, internal bacterial infections, parasites, viruses and tumors).
Although dropsy is fairly easy to diagnose, the cause is much harder to determine; however, the primary cause is usually attributed to a bacterial infection. The causative agent can be introduced to the aquarium through food, poor water quality or through the introduction of other fish to an established aquarium. Although dropsy is not highly contagious, the affected fish should be removed and placed in a quarantine aquarium. Dropsy can be spread from the affected fish, which can possibly produce stress among the other fish and make them more vulnerable to dropsy or other conditions.
Although there are no present medications that can effectively cure fish stricken with dropsy, your first line of defense is to administer a wide-spectrum antibiotic in the condition’s early stages. In addition, you might add Epsom salts to your aquarium (20 milligrams per liter or 75.2 milligrams per gallon), which will aid the affected fish in expelling unnecessary fluids from its body.
Unfortunately, the prognosis of fish affected with dropsy is not very good. By the time the fish has swollen up and the scales project outward, the internal damage may be too extensive to repair and for the fish to recover. Most cases of dropsy are fatal.
Ich, Ick or White Spot (Ichthyophthirius)
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
This is a fairly common fish disease and your local pet store should have medication you can use. 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. 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:
The most common symptom of freshwater ich (Ichthyophthirius multifiliis) is the presence of small white spots (trophonts) on the body.
The most common symptom of freshwater ich (Ichthyophthirius multifiliis) is the presence of small white spots (trophonts) on the body. Actually, these “white spots” are thickened masses of protective mucus that have covered the attacking protozoan in an attempt to dispel it. Additional symptoms include rapid breathing, cloudy eyes, possible fin deterioration and flashing. The life cycle of ich includes a host organism and the environment. The trophont is the encysted feeding stage of the parasite which enlarges, breaks through the epithelium and eventually settles on the bottom of the aquarium. When on the bottom of the aquarium, the organism, which is now referred to as a tomont, begins to undergo mitosis (cell division) and produces hundreds of ciliated theronts.
If the theronts encounter a host fish, they will attach, penetrate and enlarge (and therefore be visible to the aquarist as white spots).
In the past, I have been successful in treating ich with the use of heat. Ich thrives in a temperature range of 70 to 75 degrees Fahrenheit. The trick is to slowly increase the water temperature to approximately 86 to 88 degrees over the course of several days and leave it at this elevated temperature for approximately 10 days. The elevated water temperature is usually enough to kill the heat-sensitive theronts. A temperature above 84 degrees is the upper limit tolerated by the parasite. Owing to lower dissolved oxygen levels at elevated water temperatures, it is imperative that additional air be supplied to the aquarium using several airstones.
If you don’t want to subject the entire display aquarium to elevated water temperatures or medication that might stress plants, etc., move the fish to a quarantine aquarium for treatment. After all fish (the host animals) are removed from the display aquarium, the theronts will eventually die due to the lack of a host. Meanwhile, the infected fish can be treated using heat, malachite green, formaldehyde or a number of products available at your local pet store. Malachite green and formaldehyde do not penetrate and kill the trophonts, but instead prevent the motile tropho nts from reinfecting the fish. Ultraviolet sterilization can also be used successfully in controlling ich in its free-swimming stage; however, a UV sterilization unit is a more expensive route to take.
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.
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
Cotton like growths on the body that may appear white or gray in color.
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 Jungle Labs Binox Crystal will treat fungus problems. More information on
Hole in the Head – HITH, sometimes referred to as Head and Lateral Line Erosion – HLLE
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.
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 activated 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.
Hole in the head disease
Hexamita can build up under the skin around the head of infected specimens, which may lead to localized areas of tissue breakdown and possibly hole-in-the-head disease.
A common parasite in discus is Hexamita, which is a small parasite about the same size as a red blood cell, oval in shape, with two nuclei, six flagella on the front of the body and two flagella at the rear end. The parasite initially infects the intestines but can rapidly spread to the liver and the blood. Symptoms of discus infected by Hexamita include pale-colored, mucus like feces, loss of appetite and emaciation.
Hexamita can build up under the skin around the head of infected specimens, which may lead to localized areas of tissue breakdown and possibly hole-in-the-head disease. In untreated specimens, entire areas of skin may be undermined, resulting in large open sores. It is still debatable as to whether Hexamita is a primary or secondary cause of hole-in-the-head disease.
One of the simplest treatments for Hexamita is to slowly increase the water temperature to 86 degrees for five days, followed by a water change. The increased water temperature weakens the parasite while strengthening the discus’ immune system. If only a single specimen is infected, it should be isolated in a quarantine aquarium where the treatment is carried out. In more severe cases, dimetridazole and metronidazole have both shown to be effective against Hexamita. In the United States, products such as metrozol and other similar medications may be available at your local pet store.
Tropical fish are lethargic or resting just below the water surface and you are getting high readings on your nitrite and nitrate test kits.
Nitrite / Nitrate poisoning is not a disease but will kill your tropical fish if not remedied. 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 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.
Most or all of the fish are usually found at the water surface. They may be gulping at the surface with their mouths.
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 sunlight 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.
One or both eyes appear to be, protruding abnormally, “popping” or sticking out.
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
Pop-eye is characterized by the eye protruding from the socket, and it may appear inflamed. Pop-eye is usually caused by bacterial septicemia, tuberculosis, parasites or as a result of oxygen supersaturation of the water. Oxygen supersaturation occurs whenever the pressure of a gas in the water is higher than the pressure of the same gas in the surrounding atmosphere; the difference in gas pressures causes the gas to get pulled too quickly out of the fish’s bloodstream, leaving behind gas bubbles.
Treatment includes improving the water quality, maintaining excellent water quality thereafter and possibly reducing aeration of the water. If the cause is bacterial, treat the aquarium with a wide-spectrum antibiotic. Unfortunately, if tuberculosis or parasites are involved, the condition is usually incurable, and the individual should be removed and euthanized.
Swim Bladder Disease
Fish have a difficult time staying upright and may hang in the water. Gold Fish are especially prone to problems with the swim bladder.
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 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.
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 tan
Velvet disease in freshwater fish is caused by the protozoan Piscinoodinium. The velvet parasite is classified as a parasitic algae because it contains chlorophyll and therefore obtains some of its food through the chlorophyll. For this reason, it is often suggested to darken your tank if your fish exhibit a velvet outbreak, as chlorophyll requires visible light to survive. Velvet-infested fish exhibit small yellowish spots that are much smaller than ich spots. Similar to fish infested with ich, fish with velvet may exhibit clamped fins, and they may flash off of rocks and other surfaces in an attempt to dislodge the parasites. If the gills are affected, the fish may exhibit rapid respiration or gasp for air at the surface.
Freshwater Fish Disease
The velvet parasite has two life stages: a free-swimming form and a cyst form. The infective stage of this parasite is the free-swimming stage. During this stage, the velvet parasite has two flagella that enable it to propel itself through the water. It propels itself through the water until it finds a suitable host. Then it will attach itself to the skin or gills of the fish. Eventually, the parasite will form a cyst on the fish, which will remain on-site until it releases several hundred free-swimming Piscinoodinium. These newly released Piscinoodinium go in search of another host, and the cycle begins again. For this reason, velvet is very contagious.
Fortunately, there are effective treatments for velvet. Copper sulfate appears to be the best treatment. The only downside to using copper sulfate in your aquarium is that it will kill any invertebrates, such as snails and shrimp. In addition, it is very important not to overdose with copper sulfate, as this compound can easily poison and kill fish. Consequently, once the copper-sulfate treatment is completed, gradually change the water to remove all traces of it. The positive side to using copper sulfate is that it will also kill the ich parasite if it is present.
Consequently, you don’t need to distinguish between both parasites. Copper sulfate gets rid of all external fish parasites. Keep in mind that only the free-swimming form of the velvet parasite is affected by the copper sulfate – the encysted stage is not vulnerable to treatment. Another alternative is the use of products with acriflavine as an active ingredient; however, it may cause infertility.
If a fish has a bent or curved spine, it is most likely infected with a Gram-positive mycobacteria (Mycobacterium marinum or M. fortuitum). This is commonly referred to as fish tuberculosis, piscine tuberculosis, acid-fast disease or granuloma disease. Tuberculosis is a chronic, progressive disease that may take years to fully develop. Symptoms include lethargy, emaciation, fin and scale loss, exophthalmos (bulging eyes), skin inflammation and ulceration, edema (dropsy), peritonitis (parasite infestation) and nodules in muscles that may cause deformation of the fish. Fish that appear to be most susceptible to fish tuberculosis are gouramis, black mollies, neons, and other tetras, carp and anabantids.
Infected fish should be removed and quarantined immediately for four weeks or more. To prevent this infection, do not overcrowd, and provide good water quality. Remove any fish that appear affected. Some successful treatments have been described using chloramine-B or -T, cyclosporine, doxycycline, ethambutol, ethionamide, isoniazid, kanamycin, minocycline, penicillin, rifampin, streptomycin, sulfonamides and tetracycline. In addition, you might try using streptomycin for the first four days at a dose of 10.6 mg/L (40 mg/gallon).
After the streptomycin treatment is completed, feed the affected fish with food that has been treated (soaked in) with rifampin at a rate of 10 milligrams per 100 grams of food for about two months. At the same time, treat the aquarium with isoniazid twice a week at a 10.6 mg/L (40 mg/gallon) dosage for one month. If all fish become infected and eventually die, the entire aquarium should be sterilized using a mild bleach solution and rinsed with liberal amounts of water before adding any new fish.
If a fish has growths resembling raspberries, it may be infected with Lymphocystis. The tumors are caused by a viral infection and in some cases, a variety of environmental factors, such as poor water quality. Lymphocystis can be inherited by the parent fish or transmitted to other fish through abrasions on the skin. Lymphocystis is rarely fatal. Some hobbyists have had limited success in surgically removing the tumors and swabbing the area with some kind of iodine preparation – but there is no guarantee that they won’t grow back.
Because this is a viral infection, there is no real cure, and most people usually isolate the infected fish and let the infection run its course. Another option is to try acriflavine, which will kill plants. Therefore, in addition to following the manufacturer’s instructions, treat your fish in a quarantine aquarium if you have live plants in your display aquarium.
Grayish-white film on skin, damaged fins, ulcers, yellow to gray patches on gills, tissue on head may be eaten away.Columnaris (Cotton Wool Disease)Must be treated immediately with Over-the-counter antibiotic medications. Very contagious disinfect tank, rocks, net, etc.
Swelling of head, bulging eyes.Corynebacterioides OTC antibiotics such as penicillin and tetracycline.
Swelling of abdomen, raised scales around swollen area.Dropsy (Malawi Bloat) may be caused by internal bacterial infection (if swelling is sudden), parasites, or cancer (if swelling is gradual).Add 1/8 teaspoon of Epsom salt for every 5 gallons of water and monitor for two weeks. Check for signs of bacterial infection or parasites for further treatment.
Ragged or decaying fins. Fin rot Check pH and correct as needed. If level is normal, use OTC antibiotic for fin or tail rot.
Inactivity, loss of color or appetite, weight loss, skin defects.Fish TuberculosisHuman strength TB medication may help in early stages. Contagious disinfect tank, rocks, net, etc. to prevent transmission. Wash hands and surfaces well.
Erratic swimming, bloating or swelling in body, black patches on body or fins.Myxobacteriosis — rare Medications, if any, are difficult to come by. Keep up on water maintenance to prevent it.
Sluggishness, lack of appetite, fin damage, reddish discoloration, bulging eyes, clamped fins Septicemia Antibiotic treatment in food form is required.
White or gray fungus on eyes.Cataracts OTC medication for fungus.
White or gray patches resembling cotton, excess mucus.Mouth or Body Fungus OTC medication for fungus. Usually added to water, but may need direct application.
White cotton-like patches on fins, body, or mouth.True Fungus (Saprolegnia)OTC medication for fungus. Check for symptoms of other illnesses.
Small string-like worms visible on fish, or burrowed in skin.Anchor Worm Over-the-counter medication for parasites.
Bluish-white film on body, strained breathing caused by gill damage, peeling skin.Chilodonella Salt treatment (see below).
Weight loss, strained breathing.Copepods OTC medication for parasites, also fungal treatment for possible secondary infection on damaged gills
White film, reddened areas on body, abnormal swimming, scratching, folded fins.Costia (Slime Disease)Must be treated quickly. Raise water temperature and use OTC medication for parasites. Salt treatment may work, as well.
Weight loss, abnormal swimming, generally looks very ill. Will accompany or follow leech infestation.Blood Flagellates (Sleeping Sickness) rareSalt treatment can be used to kill leeches, but may not cure flagellates.
Sluggishness, flashing, spider web lesions on skin, color loss, reddened fins, drooping fins, fin damage.Skin Flukes (Gyrodactylus)OTC medication for parasites
Lack of appetite, weight loss, small holes or eroding pits appearing in the head.Hole in Head Disease (Hexamita) more common in cichlidsOTC medication for Hole in Head Disease.
Scratching, white salt-like spots starting on head and spreading over whole body, rapid breathing, cloudiness on eyes or fins.Ich (Ichtyophthirius) very commonOTC medication for Ich or Ick.
Scratching, small worms hanging from body.LeechSalt treatment or OTC medication for parasites.
Scratching, green to brown lice (up to inch) visible on skin.LiceOTC treatment for parasites.
Erratic swimming, weight loss, loss of color.Neon Tetra Disease mostly affects tetras, danios, and barbsTreatment is difficult look for a medication that treats gram-negative bacteria or with nalidixic acid as the active ingredient.
Darting, scratching, small yellow to white spots dusting skin.OodiniumOTC treatment for parasites.
Cloudy appearance on skin, red patches on skin where parasite has bitten.Trichodina — predominately freshwaterSalt treatment.
Red or bloody gills, gasping for air.Ammonia PoisoningNo treatment. Regular water testing and maintenance will prevent it.
Small dark spots on fins and body.Black SpotOTC medication for parasites. Spots (cysts) may remain after treatment.
Also, Cloudy white appearance to one or both eyes. Cloudy Eye Check for symptoms of another illness like velvet, ich, or tuberculosis. Treat with OTC medication.
String of feces hanging from fish, swollen abdomen, sluggishness, disinterest in food, off-balance swimming.ConstipationStop feeding for 2-3 days and continue with a more varied diet including live and plant-based foods.
Small white spots that get larger over time possibly with black streaks.Fish PoxNo treatment. Keep up on water maintenance and symptoms should cease after about 10-12 weeks.
Difficulty swimming, swimming upside-down, floating, unable to surface. Do not confuse with swim bladder disease.Flipover Air can be removed from swim bladder by a veterinarian. Surgery is also a possibility in larger fish. Check for signs of internal infection or parasites and treat as necessary.
Reddening on or under skin, sudden abnormal behavior. Inflammation OTC antibiotic treatment.
Unusually bulging of one or both eyes.Pop-eye (Exophthalmia)OTC medication for bacterial infections and/or parasites. Check for other symptoms of bacterial or parasitic infections.
Fish struggles to swim, may float with head tipped down, or have difficulty surfacing, no balance, etc. May occur after eating.Swim Bladder Disease Stop feeding for 3-4 days. If symptoms persist, feed the affected fish a small amount of fresh spinach or a green pea without the skin (laxatives).
Swelling or distention for internal tumors, external can be seen growing on skin.Tumors Usually incurable. Consult a veterinarian about potassium iodide treatment for thyroid tumors.
Sluggishness, lack of appetite, open sores with red edges, possible fin rot.Ulcers OTC medication for bacterial infections.
Scratching, small gold to white spots, loss of color, weight loss, difficulty breathing due to gill damage.Velvet (Gold Dust Disease) OTC medication for parasites.
Freshwater Fish Disease
Understand that while salt is frequently used as a treatment/preventative for sick fish, it is no guarantee. It can even be dangerous to some fish (for example, cory catfish).
There is nothing more important than maintaining a proper environment (temperature, water quality, aeration).
Basically, salt will strip or re-stimulate (depending upon the concentration) the slime coat produced by the fish, increasing antibodies and making bacteria, fungus, and parasites more vulnerable to medications such as antibiotics or fungicides.
The following salts can be used in a salt treatment for your fish: Aquarium, solar (without anti-caking additives), meat curing, sea, kosher, rock, pickling, and ice cream salts, or regular non-iodized table salt.The additives mentioned above may include a type known as sodium ferrocyanide or yellow prussiate of soda. This is deadly to fish. The “cyanide” part should clue you into that.
For a constant preventative treatment, use a low concentration of about .3%. This is equal to about 2.5 teaspoons per U.S. gallon of water. If you have live plants in your aquarium, you may want to consider about half that amount.
For a concentrated “dip” to be used in treatment of external parasites, the concentration should be 1%, or 7.5 teaspoons per U.S. gallon. You must be very careful when using these dips. All fish will react differently to salt treatments, and especially smaller fish must be monitored very closely. Generally this will be done in a hospital/quarantine tank, as water changes are the only way to remove salt from your main tank. The hospital/quarantine tank should be at least one gallon, with no rocks and only two or three plastic plants for security. The temperature should be kept between 75-80 degrees with good aeration.
Dissolve your salt completely before adding your fish. Once you have put your fish into the water, watch it closely for signs of distress, such as rolling over. This may be as quickly as a few seconds with smaller or baby fish. Remove the fish at the first sign! Do not leave your fish in this solution longer than 30 minutes. Then place it in a container of aged water, preferably not taken from the main (still infected) tank. Give the tank a thorough cleaning while your fish recuperates.
A quarantine aquarium is inexpensive to operate and can be set up easily. I suspect that most hobbyists have the necessary equipment. For the vast majority of freshwater aquarists, a 10-gallon aquarium with a sponge filter, heater, and short sections of PVC pipe or plastic flowerpots to provide ample hiding places are sufficient, unless of course you are maintaining some of the larger freshwater species.
While fish are held in quarantine, excellent water quality must be maintained in respect to pH and nitrogenous waste levels. Although the ammonia and nitrite levels should be zero if the sponge filter has a sufficient culture of beneficial bacteria (Nitrosomonas and Nitrobacter), the nitrate level and proper pH can easily be maintained through frequent water changes. When performing these water changes, it is important that the pH and temperature do not fluctuate, in order to avoid further stress.
In general, quarantining fish for 30 to 60 days will prevent introducing most parasites into the aquarium. During this period, water changes alone will assist in eliminating the parasites by dilution and minimizing reinfection. Some suggest keeping freshwater fish in saltwater (3 to 5 parts per thousand) during quarantine, as this will aid in eliminating any pathogens that are not salt-tolerant. In addition, it will help fish maintain their fluid balance. For the most part, I don’t use an antibiotic, but if a particular specimen shows early signs of disease, I will occasionally use a wide-spectrum antibiotic or formalin. The latter is also useful in eliminating protozoa.
So the next time you walk by your aquarium and see something amiss, you should be able to react quickly and make educated guesses as to how to treat your fish. Quarantine your fish, and perform regular partial water changes. Also observe your fish often to avoid these most common diseases in the first place.