Common Diseases for Tropical Fish and Cichlids.

Ick

Tiny white spots will appear on your fish, and your fish may start itching or rubbing.
It is a parasite, tiny and spreads like no tomorrow. The parasite burrows right under your fish's skin, and then developed into the little white spot or cyst, that eventually falls off, sinks, and breaks open, letting thousands of little "hair like" organisms out that. These swim upward, bury them selves under your fishes skin and repeat the process. It spreads fast and strong.

Chill may weaken your fish and ick may appear, or something introduced, fish, decoration out of another tank, or used gravel also can be hosts to ick.

To treat ick, crank the heat up, it shortens the life cycle of the parasite (which can live for a long time in colder aquariums). Also there are commercial treatments available that you add to your water, most often the active ingredient is methylene blue, which is a blue dye. Seal salt will also work, I haven't tried it, but have been told one teaspoon to gallon of water, use at your risk, I can't guarantee the effects. Sea salt in low doses will not harm fresh water fish when added incrementally. (house salts contains iodine which is deadly to fish never add it to your tank).
Methylene blue, or a “some name brand” treatment that contains a similar dye is very effective. It doesn't kill the parasite when it is on your fish but when the cyst drops it inhibits the "hair like" organisms from infecting your fish, with heat it will rid your tank of ick, but be sure to thoroughly vacuum your gravel and then disinfect your siphon and any nets you have used in the infected water. (Infected nets, decorations, siphons, ect . . . can infect other tanks, or re-infect a treated tank.

Some people will tell you to remove the infected fish immediately, but in all honestly if you see the spots and remove the fish, treat the whole tank anyway, more than likely it has started to spread. With the dye there are some side effects, certain kinds of treatment can be harmful to your fish if you use a carbon filter (the filter can also trap ick so toss it out) so removing your filter during treatment is necessary. Methylene blue will also kill plants, which I would destroy after an ick infestation to be better safe than sorry anyway. Lastly the silicone caulking may become bluish, from the dye.

Dropsy

It is a horrible disease, your fish's scales will become angled and almost stand up, the body can be puffy, or just puffy in places, eyes can bulge, and the mouths can become deformed as if infected by tumors.

Cause is not 100% known, there are commercial treatments but I have not seen one work yet.
It is suggested to remove the fish immediately, it is not known to spread and seems to be random on the fish it targets, but better safe than sorry. You can try commercial treatments, but in the end you may have to put your fish down. I will cover that at the end of this "article" if you will call it that.

Pop-eyes

Something has caused a hemorrhage behind the fish's eye. The eye, or both eyes bulge and maybe discolored.

This could have many causes, infection, fighting, stress, or bumping into a decoration.
Sea salt will treat this, start with one tsp per gallon for two days, if no relief use two tsp per gallon on day three. Change water after treatment a bit by bit, not all at once. Also silversol or a similar product on a q-tip rubbed on the fish's eye (gently) is a cure, for this you must catch the fish in a net and apply. Also time may heal this if your fish isn't too upset or distressed, it maybe better to wait and see how it heals.

Fungus, fin rot or mouth rot

This disease is deadly, and will kill fish quickly.
A bit of white fluffy looking material will appear on the mouth or fins and starts to eat the flesh of the fish. It will spread very quickly, and can devastate a tank in no time.
There are commercial cures, most likely aureomycin is the active ingredient, it is very expensive in some locations.

50mg per gallon will cure the rot in a couple days, fish severely infected still may not survive, separate at the first sign to prevent spreading, and cross your fingers.

Velvet

This is caused by a protozoan that infects the fish. The proto has a free swimming stage so it is best killed during this vulnerable part of it's life.
A film covers part of your fish, it will be yellow or brownish, some itching may occur. More spots will appear if not treated, and the older spots may become hard and rust like.
Fry infected will die from velvet 99% of the time, smaller fish are also more at risk to die from velvet.

To treat velvet commercial cures are available, most are dye treatments and may contain acriflavine. Since they are dye treatments plants should be removed, and disinfected returned after treatment is done, also your charcoal filters must be removed. Many commercial products may treat ick and velvet, as both respond to dye treatments.

Swim Bladder Disorders

Your fish has a bladder inside it filled with gas, it controls the rise or sink of the fish. If your fish is floating (and not dead) it may have a swim bladder disorder.

The bad news! This is rare and incurable the fish should be put down. The good news! Most times (unless something fell on your fish, or you squeezed it) this is simply caused by indigestion. Do not feed for two-three days and if the situation improves you may have to change your food.

Flukes

Caused by gyrodactylus, a parasite that sticks itself in the gills and skin.
This is not often seen but symptoms are a fish that darts around stops all of the sudden, looking as if exhausted. Flukes is highly contagious, hard to get out of a tank, and can cause enough stress to kill a healthy fish. Good news is it treatable.
Commercial treatments are available, but can be hard to find in certain areas. I'd suggest getting one to use. If not you can treat the fish yourself, but it is difficult.

Remove the fish into another tank (or fishy hospital tank as some call it) as it is highly contagious. Always have another treatment tank available even if it is a Tupperware container.
You can treat flukes with glacial acetic acid at one drop per ounce. Place your fish in this mixture for 15-20 seconds, and repeat every two days (not over three treatments)
If you can't find glacial acetic acid, and you can find formaldehyde then you can put 15-20 drops into a gallon of water an place the fish in until it looks tired or exhausted, usually less than 10 minutes, and repeat just like the glacial acetic treatment.

Notes

If you use a dye treatment remove the charcoal filter!
Sea salt is relatively safe for fresh water fish, not table or house salt ,iodine will kill your fish! One tsp per gallon is the recommending starting dose, though most fish can handle 2-3 tsp per gallon. If you use salt try and use a separate tank or container, as salt is hard on plants and may kill them. Also plecostomus and snails are not very tolerant to salt. It is also better to change the salt water out gradually back to fresh water, a completely change may stress or cause stress in the fish.

To put down a fish humanely;

Put your fish in a separate container, less than one gallon if possible. Add clove oil to the water, add until your fish stops or barely moves. Clove oil is an anesthetic, and is commonly used in fish surgeries, it will numb and make sure your fish feels no pain. When your fish is very numb and barely moving add grain alcohol to the water, a good amount. This will ensure your fish doesn't wake up. If you use clove oil alone the fish may recover and spring back to live after the effects wear off, but it is possible to euthanize a fish with just clove oil. If you have no gill movements for 2 minutes then your fish has expired.