A Closer Look at Black Spot Disease - Part 1 (Ammonia)
There are two very different fish diseases that get called ‘black spot disease.’ One is caused by healing after injury (most commonly ammonia burn), and the other is caused by a parasite that infects the intestine of birds.
Ammonia burn
Most examples of black spot disease in aquariums are the result of ammonia burn on the fish’s skin or fins. When the affected areas start to heal, the small patches that recieved the harshest burn turn a dark brown or black colour.
The black spots themselves appear as discoloration of the skin, rather than something in or on the skin. They can range in size from barely noticeable to a “rolled around in black paint” look, but are usually small smudges.
Blackened skin from ammonia burn is actually a good sign. It means the ammonia has dropped back to a safe level, and the fish’s skin has started to heal.
However, it is a worrying sign that the ammonia level was raised in the first place. Action needs to be taken to minimize the risk of raised ammonia. A lot of fish that suffer ammonia burn don’t get the chance to get black patches on their skin. They get killed instead.
Spot the signs
Fish in a tank or pond with high levels of ammonia will gasp for oxygen at the surface, float on their sides, sit at the bottom, lose their appetite, get red streaks in their fins, develop reddening around the gills, and/or make swimming look like hard work.
As soon as any of these behaviours are spotted, get the water tested to confirm ammonia poisoning and take action to remove it.
Removing ammonia
Changing the water is the best way to get rid of ammonia. Do it every day until the ammonia levels are down to an acceptable level i.e. less than 4 parts per million. An ideal level is less than 2 parts per million.
The other option is to use chemical treatment, but water changes are obviously better as they do not involve adding further chemicals to the water.
Prevention
Test the water regularly, and change it regularly. High ammonia levels are a sign of a badly managed aquarium.
Do not overstock. Too many fish produce too much waste, which contains ammonia. If the filter can’t cope, ammonia poisoning is inevitable.
Do not overfeed. Uneaten food decays, producing ammonia.
Use a treatment tank if the water needs to be medicated. Medications for unrelated fish diseases can kill the bacteria in the filter that remove ammonia from the water.
Keep a very close eye on new tanks. Ammonia poisoning occurs most often in new tanks. Ammonia will peak at the end of the first week. It is advisable to start with only one fish so waste is kept to a minimum.
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June 13th, 2009 at 7:15 am
This is a great article that should be promoted much more. Unfortunately, this characteristic of goldfish is not well known to people and surprisingly a large amount pet store keepers.