Appearance:

Worms & Bugs—Worm- or bug-like protrusions are not normal and should be given immediate attention.

Fish Lice-look small (¼ inch), semi-transparent, lacy circles and can be found anywhere on the fish’s body. They can be removed by very carefully restraining the fish and gently scraping the louse off if the fish is large enough and can tolerate gentle handling, or you can treat with an external parasite medication.

Anchor Worms are recognized by white worm-like protrusions that can be found anywhere on the fish’s body. They can be removed by very carefully restraining the fish and using tweezers to gently remove the anchor-like head from beneath the fish’s scales or by treating with an external parasite medication.

Camallanus are red worms that can be seen protruding from the anus of the fish, especially after eating and when the fish is at rest. From what I’ve seen, livebearers and Gourami seem to be the most susceptible to it. It is very difficult to treat and multiplies using an invertebrate as a host. Destroy infected fish and medicate to (hopefully) kill hosts and larvae. (or you can tear down your tank, sterilize your equipment, and start over). If you leave exposed fish in the tank, wait a few months before adding new fish.

White spots—Ick is a very common parasite that often attacks sick, stressed, or weakened fish. It looks like small salt crystals have been sprinkled over the fish’s body. If caught very early (only two or three parasites visible) it can often be treated by adding freshwater aquarium salt to the tank—roughly 1-Tablespoon to 5 gallons of water. Ick medications are very effective at destroying this parasite. Treatments won’t kill this parasite though until it drops off after several hours or days (depending on tank temperature) to reproduce. The medication actually prevents re-infestations.

White, Milky Slime—Patches of milky slime on the body or eye of your fish usually indicate a bacterial infection which should be treated with an antibiotic. Such patches can also be caused by small external parasites. You would need a microscope for an accurate diagnosis, but if the infection doesn’t seem to respond to antibiotics, try treating for external parasites.

White Nodule—Lymph, a viral infection, is often found on the fins. It looks like a tiny piece of cauliflower. It can often be left untreated, or may be gently removed manually.

White Fuzzy Patches—Fungal infections are usually easy to recognize by their white, cottony appearance. They are commonly secondary infections of open wounds and can be found anywhere on the body of the fish. Eggs may also develop fungal infections. Treat with anti-fungal medication. Preventative medication is often used when eggs are present. Columnaris is a bacterial infection that is usually found on the mouth of the fish, often called cotton mouth. It may respond to antibiotic treatments.

Ragged Fins—Fin rot may be fungal or bacterial. A bacterial infection will have a more stringy appearance while a fungal infection will look smoother (though still jagged) and may appear as a white border on the fins. Use appropriate medication. Some medications will treat both. Fin damage may also be a sign of Tuberculosis.

Bloody Streaks-Septicemia is a bacterial infection that causes bloody streaks or patches on the skin of the fish. It should be treated with an antibiotic. Bloody patches may also be present due to injuries or parasites such as fish lice.

Red, Swollen Gills—Red swollen gills may be caused by gill damage due to ammonia poisoning or other toxins present in the water. Check water conditions, partial water changes may be necessary. A parasitic gill infection, such as gill flukes, will also cause swelling and should be treated with a parasite medication.

Yellow Powder—Velvet is an external parasite, similar to ick, but the parasites are smaller and yellowish in color. The fish will often look like he has been dusted with yellow powder. Treat immediately for external parasites.

Color Changes—It is normal for a fish to change colors. They will fade to blend in to a dark background and will often fade at night or when they are under stress, though some fish turn almost black when they are under stress. Colors often intensify at feeding time, or when a fish is breeding or fighting. A brightly colored fish may lose its color over time if the diet is inappropriate. Things to worry about are patches of dark or light coloration (though stress coloration is also a worry if it is prolonged because stress makes the fish susceptible to infections). White patches may indicate bacterial or fungal infections (see milky white or fuzzy white patches). Bacterial infections include illness such as true and false neon-tetra diseases (both of which cause opaque white patches under the skin and are incurable), and Columnaris (see white fuzzy patches). Darkened areas may indicate cancer or damage to the nervous system from injury or parasites.

Sunken Belly—If the fish is eating and continues to lose weight, there is probably an internal parasite present, especially if the waste is stringy. If he is not eating and appears emaciated, his loss of appetite may be caused by parasites or by something else. A sunken belly may also be caused by Tuberculosis. Try to identify other symptoms. (Make sure that you are feeding the fish an appropriate diet—some of these guys are very picky)

Stringy Poop—A good sign that there is an internal parasite present is stringy, whitish poop. Normal waste should be solid looking, opaque, and a color that reflects what the fish is being fed (mostly shades of brown and green).

Misshapen Spine—A bent spine is a common birth defect, but if a fish suddenly develops a bent spine, poor nutrition from an inadequate diet or Tuberculosis may be the cause.

Protruding Eye—Popeye may be caused by Tuberculosis or by another infection. Look for other symptoms. There are medications which claim to treat popeye and may be worth a try. If Tuberculosis is the cause, there is little to be done in the way of treatment. Under good water conditions, the fish may live some time.   Chilling the water and adding salt will often prove a useful remedy if it is not Tuberculosis.

Swollen Belly—Females with eggs can have large bellies, as can fish who have overeaten. If the belly is very large, especially if the scales are protruding, suspect Dropsy. This is a serious bacterial infection which will be difficult to treat, but may respond to antibiotics. Swelling may also be caused by internal parasites or by Tuberculosis.

Protruding Scales—If your fish takes on a fuzzy appearance as if all the scales are sticking out instead of laying flat against the body, the fish likely has Dropsy. In this disease, the belly will also be swollen. This is a serious bacterial infection which will be difficult to treat, but may respond to antibiotics.

Holes—Sometimes sensory pores in the face and sides of a fish become irritated and the holes become enlarged. This condition is often referred to as Hole in the Head, or lateral line disease. It affects mostly large fish such as Oscars. The cause is uncertain, but water conditions play a very significant role in the development (and sometimes treatment) of this problem. Large fish need a lot of space (way more than a gallon per inch) and it can be very difficult to keep the water clean. Very frequent (maybe daily) water changes may help this condition once it has appeared, and can do a lot to prevent it in the first place.

Scales Falling Off—Loss of scales is usually due to a mechanical injury. Keep the water good and the fish healthy and they will grow back.

Lumps and Bumps—fish too can contract cancer. External tumors may be malignant or benign and will look like boils on the fish’s body. Internal tumors may also occur. Some thyroid tumors can be treated, but most tumors cannot.