To avoid future problems, it is better to adopt preventive measures, which will help us to keep our animals from catching a disease. We must be able to distinguish diseases that are originated by the conditions of our aquarium from the ones that comes from fungi, parasites, bacteria or virus.

We must do an especial effort keeping our aquarium conditions optimally:

Control pH, hardness, ammonia and nitrite values.
Watch water temperature.
Feed the fish with a varied alimentation is one of the pillars to prevent a lot of diseases.
Regularly change the water, remembering that it is not the same to replace the evaporated water than change the water.
Clean up the filters regularly; if we notice that the water acidifies alarmingly, it probably means that the filter needs to be cleaned up. Do not forget to always leave a part of the old filter and change only half of the filtrating matter, and next time change the other half.
Eliminate dead plants and of course, dead fish. If we have an “infirmary aquarium” we should put there any fish that we suspect to be sick. A very good prophylactic measure is to take out a fish before it dies (when we notice it is sick); it is better to take it out, put it in a small container and let it die there.
Siphoned the bottom of the aquarium two or three times a year, but do not do it all at once, siphon half of the surface and then the other half 15 days later, this way the bacterial colony will have had time to recover.
We must be sure that any wires, clamps or other objects we put in contact with the water are perfectly clean, and if we use them in different fish globes, we must not forget to disinfect them.
And last, we must never be too confident when everything goes well, because if we relax too much, lower our guard and forget to keep doing the necessary cares, well…….. :-(( … things can end badly.
Let us remember the Murphy law: “If something can go wrong, it will go wrong”

And its corollaries “When things are left at random, they usually go from bad to worse” or “If there is a chance of several things going wrong, the one that causes more damage will be the only one that will happen”.


Tuberculosis has the Mycobacterium marinum as its causing agent. Infected fish have several degenerative symptoms such as sunken belly, torn fins and ulcerate skin. The best thing to do is to get rid of the infected fish given that their treatment is a very prolonged one.  If you decide to treat the fish that are infected, the product you must use is “isoniacida”, distributed to the fish with their food, as we have described for antibiotic treatment, or added to the water at 40 mg every four liters, repeating every three days changing 25% of the water. The healing process may last two month.

Any kind of cyst is usually cause by spore forming protozoa and we can not heal it with the knowledge we have acquired so far. The more common causing agents are the Henneguya, Plistophora and Glugea species. The only fungi infection known in fish is the Ichthyosporidium hoferi, an organism that attacks fish’s liver and kidneys, and later on it spreads all over their bodies. The first visible marks are some brown cysts on the skin. There are no safe treatments for this disease, so the best thing to do is to get rid of the sick fish, although some infected fish are able to assimilate the disease and can live with it indefinitely.

The vermes are an occasional disturbance, being the Benedenia melleni the more common one. They live on fish’s skin and gills, and can grow to a millimeter, causing malaise and even open wounds. The treatment used to cure this disease it is a very difficult one; the bests published results show the use of pesticides like Dibrom, Dipterex and Dilos (they all have Trichlorfon) at doses of about 0.25 ppm (0.25 mg per liter). They are mixed with four liters of water from the fish globe and are added gradually into the aquarium. The same treatment can be used on water flea and copepods.

The velvet, or chorale fish disease, it is characterized by a tendency on the fish to rub themselves against objects inside the aquarium, a fast breathing and practically folded fins. On a more detailed inspection of the animals we can see how fish are cover by a dusty layer on the surface of their bodies, which is hard to see unless it is under an oblique light. The cause for this disease is the Amyloodinium ocellatum, a protozoa that resides on fish’s  gills and body surface, after a swimming freely stage, where it forms cysts, that produces more free forms.  Treatment with copper sulfate or citrate must go on for about 10 days, keeping a concentration of about 0.15 parts per million(ppm or mg per liter),  On sea water, copper is rapidly eliminated from the solution and gets fixed on the substratum or the chorale, therefore, the concentration must be controlled with a copper kit. If you don not use the kit, half a dose every two days added to the water may be enough to keep the copper level under toxic rates, which starts at 0.4 ppm.

The white spot is another infection on skin and gills. It is caused by the Cryptocaryon irritans protozoa. As the velvet, it has a swimming stage, where it is easier to eliminate it. The free tomites are deposited on the fish and develop inside a white cyst that can have 1 millimeter of diameter. This irritates fish and produces a similar behavior on fish than the one velvet causes. It is recommended a copper treatment as well.

Bacterial diseases can produce red areas on the body or fins, and if they are not treated, can turn into ulcers and putrefaction of the fins and tail. There are a lot of bacterial species that can cause this, and the best treatment is administration of antibiotics with the food (as long as fish are able to eat). Mix Chloromycetin preferably or any other antibiotic of wide spectrum at 1% along with the appropriate food, and distribute it twice a day. If fish are not eating, treat the whole fish globe with 50 -100 mg of antibiotic every four liters of water and disconnect the biological filter. Do not use aureomycin that forms foam and turns red.



Toxicity of the materials: problems caused by objects that should not be inside the aquarium. Paints, clay, dissolvent, cement, rubber, metals, etc.

Oxygen deficit: we can intuit the lack of oxygen if we see fish gasp on the surface, oxygen has very little capacity to dissolve on water and this has to do with temperature, atmospheric pressure and salinity of the water. Excess of food, organic matter and putrefaction of plants consume a lot of oxygen on their combustion process. In case of danger, air the aquarium rapidly.

Acidosis: it is cause by the acidification of water (remember that it can be caused by saturation of the filter). Fish swim in an abrupt way, gasp or can even jump outside the water. As an emergency method we can put bicarbonate on small doses (a coffee spoon per 100 liters of water) and repeat the operation after one hour and if we see that the situation persists after analyzing the water the next day we can clean the filter.

Alkalosis: this problem shows up if the pH is higher than 9, especially on soft water. It causes irritation on the gills, torn fins and darkening on the skin. We can lower the pH with any solution made for this purpose or with phosphoric acid (1 cc per 100 liters), if this does not help, repeat the operation after one hour.

Too much food: overfeeding kills, directly or indirectly, given that besides the direct problems of the fish, we will find that the levels of dissolved oxygen on water drops, we will find an increase on ammonia levels, etc. We can unbalance entirely the aquarium. Remember that it is better to feed the fish several times a day on little amounts than a big amount at once.

Ammonia NH3: highly dangerous, especially with pH levels over 7.5, given that on inferior levels ammonium (NH4) is produced, but with a higher pH the ammonium ion is lost and ammonia appears. It produces several damages on gills and different internal organs. At low levels it produces stress and at higher levels, death. If you detect ammonia you must rapidly change part of the water.

Nitrites NO2: it is the result of decomposition of ammonia because of the work of nitrosomona bacteria. It is not as dangerous as the ammonia but it can cause death by asphyxia by not letting blood transport oxygen when the nitrites mix with the hemoglobin.

Nitrates NO3: appear when the nitrobacter bacteria decompose the nitrite. It is very dangerous to sea fish and it is hardly toxic for sweet water fish. It can be eliminate by changing part of the water and also because of their absorption on plants.

Chlorine: chlorine does not kill instantly, it slowly degenerate gills until death on high concentrations.

Electricity: if we have any leak of electricity this may cause electrolysis producing undesired metallic salts.

Blow on the glass: be very careful hitting the glass of the fish globe, the waves that this causes inside may kill a fish or cause them stress.


Tuberculosis: there are different symptoms, such as loss of appetite, emaciation, bulging eyes, fall of the eyes, degeneration of the vertebral column, defects on the grudges. Contamination travels through digestive area. There is no applicable treatment given to the variety of existing stumps.

Hydropsy: it can be caused by bacteria or virus. Symptoms are: swelling of the eyes, excelled and blush anus, inflated body and open grudges. It is hard to cure with medication.

Sepsis: it causes hemorrhage on fish’s skin; this disease is transported by the blood. It manifests so fast that it is almost impossible to treat it.

Columnaris: also known as “mouth fungus”, presents grey-white spots on fish’s head, fins, nutgalls and other parts of the body. It is very dangerous when affects gills. There are some forms that do not present external manifestations. It is rapidly propagate.

Putrefaction of the fins: it starts with a light turbid on the fins, then they start disintegrating and get shorter every day, presenting a torn aspect, and finally only the base of the fins survives. Frequently there are also fungus attacks on the fins. An increase of temperature along with a good hygiene, are a very good remedy.


Lymphocystis: usually appears on fins and then it spreads all over the body. They are white protuberances brambleberry shaped; they are also presented as pearl threads. It is commonly confused with fungus affection. It is more frequently presented on the anabantidos family. There are no remedies for this disease, it is preferable to separate the sick fish and even cut off the infected piece of fin. You can put iodine dye on the affected areas. After two month you can be sure that no other fish has been infected, because during that whole time the virus can still infect fish.

Hydropsy: as we have mentioned before, this disease can be caused by a bacteria or a virus.


Siprolegnia: the affected parts seem to be covered by cotton, it can happen on the skin, nutgalls, mouth, fins and even the eyes can be attacked. If the attack is superficial the problem can be solved without any complications, but if the fungus filaments have damage internal parts of the fish, it is very hard to control it, besides it opens the door to an important number of secondary infections.

Mycosis on gills: they are fungus that attacks gills. If it is not stopped rapidly it can kill a fish by necrosis.


Ictioftitiasis: white spot, it is the most usual parasite. The white spot we see it is actually a reaction caused by the parasite on the fish skin, it is not the parasite itself. It starts on fins and then spreads to the rest of the body.  It is a disease typical of sudden changes of temperature, given that the fish are more inclined to suffer stress which makes them weak. Besides the appropriate treatment with medication it is recommended to raise the temperature and air the water.

Oodinium: velvet disease, it is characterized by an off-white color layer that covers fish’s body, observed in a microscope one see that it really is just a multitude of tiny little unicellular parasites. It causes a lot of damage on skin and nutgalls, the fish may die from asphyxia due to the damage caused on the gills.

Costiasis: it attacks fish’s mucous, at first one can see on the skin and gills little areas covered by a grey veil, later on red hemorrhagic areas are observed, produced by flagellate (Costia necatrix). Raise the temperature and air the water strongly are a good remedy accompany by an appropriate medication.

Chilodonella: usually acts as an over-infection, attacking skin and gills. It can be treated like the Costiasis.

Trichodiniasis: usually behaves as a secondary parasite, only occasionally shows up as a primary pathology. It usually accompanies the Ictioftitiasis (white spot). One can not see it at plain sight, affected fish loss weight and breathe air from the surface.


Plistophorosis: also known as “Neon disease”. Affected fish lose coloration and on the color stripes appear off-white spots. Fish swim stunned with abrupt movements, sometimes there are vertebral deformations, sick fish separate themselves from the rest of the fish of their specie and at night they can not stop swimming. We must remove the sick fish rapidly. There are no clear methods to heal this disease.

Hexamitosis: the Hexamita is a flagellate protozoon that lives on some specie’s intestines, when due any cause the fish gets debilitated, there can be abnormal growth of these parasites colonies, and they invade the intestine and then all of the body towards the exterior. Symptoms are: great loss of weight and darkening of the skin. There are some products that mix along with the food can cure this disease.

Let us remember that the hygiene measures, prophylaxis and cares that were explained at the beginning of these pages are of great value to avoid a lot of diseases, it makes no sense to kill pathogen agents when these can be produced by a pour filtration or maintenance of our aquarium. However, it is not recommended to abuse of antibiotics or any kind of medication, due that antibiotic debilitate fish and we may get healthy fish sick by debilitate them with unnecessary antibiotic treatments.

Most diseases and parasites are present in our aquarium on a latent form; they are only waiting for the propitious conditions to manifest themselves. The presence of a disease is not always caused by an incorporation of a foreign specimen, what sometimes happens is that the fish we already have in the aquarium are somehow immune to certain stumps and when we introduce new specimens with immunity to other stumps, all fish may develop that disease.

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