If one takes necessary precautions before fish get sick, it is very unlikely to face problems. It is essential to apply a healthy and appropriate diet on fish. Moreover, the water quality in the aquarium should be at a high and stable level. One should avoid behaviors that would make fish stressed as these would lead to weaken their immune system. Indeed, sudden water level changes and poor-quality water would trigger the pests in their bodies, and owing to pests’ effects on weakening fish’s immune system, the fish would be susceptible to sicknesses. Aquarium temperature, pH, GH, KH, NH3, NH4, NO2 are of great importance with regard to this issue. These ratios should be kept stable. Discus is a different kind of fish that demonstrates its discomfort clearly and immediately among other aquarium fish and it is the quickest to respond to the treatments. Thus, one has to be a good observer in the determination of sicknesses and analyzing treatments. It is vital not to be impatient and essential to diagnose correctly. Also, it is necessary not to be careless and one has to be quick to start treatment. Personally, I do not start the treatment before observing the fish for four days, and during this period I try to get water conditions to the most suitable level which is also in high quality. Most of the time, good water conditions are enough for the treatment. I, also, would like to underscore quarantine aquarium as a strong part for the treatment.

Bacterial Infections,
-Pseudomonas fluorescens
-Chondrococcus columnaris
-Aeromonas hydrophila
-Aeromonas salmonicida
-Myxobacteriosis

COLUMNARIS, The bacteria leading to this illness is quite sticky. These bacteria hole roundly in the body. Around these holes, one can see a yellow and sticky material. This material can be seen more clearly in high temperature, and less clearly in low temperature. If this material picks on the branchias, capillaries will be affected and this will result in asphyxia, and eventually death of fish.

It is crucial to observe with microscope in the cases where bacteria result in bacterial infections. If the responsible bacterium is found, it will be easier to choose the appropriate antibiotics for the treatment. The best method to be used in the treatment is the usage of an antibiotic with a large-spectrum and a content of gram-positive and gram-negative. Another method to be used in the treatments of bacterial infections is to lower the pH level. However, this method entails high level experience and it is applied with decreases in decreases in pH in steps. 

Fungal Infections,

Thrush is generally formed as a result of fungus. Fungus saprolegnia is the most common one in aquariums. One must think about the factor behind in fungal infections as existing funguses in water are not detrimental to a healthy fish. In general, funguses are not contagious; therefore, if more than one fish suffer from thrush-wise problems,this may be a bacterial problem, or it may be water conditions that affect plenty of fish. If one can hold fish with hand, and if the area with fungus is far from branchias, use some cotton with some iodize tincture or methylene blue, and without pressuring on the area apply the treatment away from the blanchias. If the fish is too small or the fungus is too dispersed, put 2 drops of methylene blue for 10 litres to treatment tank, and change the water after 24 hours, if the problem goes on, reapply the process.

-Saprolegnia

-Ichthyosporidium

-Fungal cataract

Mould Infections

-Oomycetes

Parasitic Illness

-Gyrodactylus salaris

GYRODACTYLUS 

It has a pair of anchors and 16 hooks on the both sides. Under suitable conditions, it is apparent. This external parasite causes weakness, depreciation in blanchias, making the skin mat, glowing in different parts of the fish. It settles on the skin and blanchias, and leads to death of fish.

-Dactylogyrus

Blanchia Worm is the most common parasitic illness. Gyrodactylus and Dactylogyrus are the most common ones. These parasites are very effective and deadly on baby and young discus. Permasol or formaline bath could be effective for treatment. 

-Protozoa

.Costia, It is the parasite that causes sickness in the skin and blanchia. It swims randomly and moves with its long flagellums. In advanced cases, skin of fish gets a mucus-wise form. One can observe unwillingness in fish’s movements and feeding. If not treated, it may lead to death.

.Ichthyophthirius

Sometimes there emerged blots on skins, and this can attributed to Costia or Ichtyophthirius.

.Cryptocaryon

.Oodinium

It resembles to the sickness “white freckles”. However, it is much smaller than that and it leaves a form on the fish that is quite like a white dustcloud. If not treated, it may result in death, too.

.Trypanosoma

.Velvet

.Hexamita

It is an active, 8-flagellumed parasite that lives in the intestine of fish. It results in a typical sickness, especially in discus. One can observe slimming, anorexia, and sudden swimming moves in fish.

.Capillaria

Two main intestine parasites are Hexamita and Capillaria. The discus attacked intensively by these two parasites demonstrates anorexia, slimming and defecation of white, long, gel-wise stools.    .

.Glugea

.Henneguya

.Chilodonella

-Myxosporea

-Microspora

-Helmintic

-Crustaceans