Hyper-Melanization
Those small black smudges on the Anemonefish are reactions of the fish coming into contact with a marine lifeform that is irritating their skin. The result is the condition known as Hyper-Melanization. You can find sample photos of fishes with this condition on the Internet. What you may not find is proper guidance about what to do about it.
Talk about irritation! There seems to be some confusion about what the fish is going through. There are hobbyists, which I must admit irritate me, that say, 'Ignore it and it should go away.' That irritates me because the fish is being harmed by the contact it has with some lifeform in the aquarium. So let's get some understanding here!
Just for a moment, let's talk about melanization. If a person was melaninized to the sun, we'd say they were tanned. But hyper-melaninization to the sun would be a sunburn on that person. The difference between melanization in fish is that we, hobbyists, don't see it. When we do see melanization in our fish, it has entered into the hyper state and the fish is in trouble. The point of it becoming visible to hobbyists is misunderstood. When you see it, it has gone too far.
What is happening is that the body of the fish has entered into an inflammatory response stage. The fish may be eating and to all other behavior patterns seem to be 'normal' but the body of the fish is displaying harm. This is a great photo to illustrate this: http://www.reefsanctuary.com/forums/fish-diseases-treatments/61206-clown-spotty-discoloration.html
Anemonefishes have a wonderfully thick mucous coating with allows them to handle the stinging tentacles of their host anemone. They rarely have an adverse reaction to their host anemone. However in the confines of a reef aquarium the Anemonefish faces a lot of different lifeforms unnaturally found in a small space. The Anemonefish has a strong instinct to form a relationship with an anemone and lacking this will attempt to find a 'home' in the lap of another lifeform. Even when there is an anemone available, the Anemonefish may still not host it, but try to host with one or more of the other aquarium lifeforms.
The fish isn't equipped to handle the stings of other lifeforms. Natural Selection has produced an Anemonefish that hosts with a narrow range of anemone lifeforms -- not all of which are right for each species. So when the fish tries to host with another lifeform, one that harms it, the result is Hyper-Melanization.
The irritating part is this: Hobbyists often pretend this isn't a problem. But the fish is being stung. Does the fish have to die to convince the hobbyist it is being hurt? Wake up! There is a chance that the fish mucous coating will prevail and protect the fish OR there is a chance the fish will learn to keep away from the stinging lifeform OR there is a chance the fish will continue to be harmed (in part by its need to host). Here's the guideline to follow.
1. Note the date when Hyper-Melanization is first noted;
2. Watch fish carefully, if those black smudges spread to cover over 70% of the entire body (not including fins and eyes), move the fish out or move the offending lifeform out of the aquarium (you can try A.). ALSO: move the fish out of the tank if the spots show signs of redness;
3. If 2. doesn't come about (that is the smudges don't spread to cover more than about 70% of the fish AND none of them show redness), then leave the fish in the aquarium no more than 10 days with the signs of Hyper-Melanization;
4. At the end of 10 days if the signs of Hyper-Melanization are not gone totally or diminished to some marks are faded and barely visible, then move the fish or offending lifeform out of the aquarium (you can try A.);
5. If after 3 weeks from 1. there is still even the smallest of smudge on the fish, then move the fish or the offending lifeform out of the aquarium -- for the rest of their lives.
A. You can try putting the two back together after all signs of Hyper-Melanization have left the fish, but if Hyper-Melanization is noted again, give it up and keep the two separated for the rest of their lives.
Remember, those stings were meant to irritate or kill other fishes and/or marine lifeforms. They are not something to ignore. They are not something to treat likely. I wish humans could understand what the fish is going through. The fish is being 'burned.' It isn't 'nothing' to that fish regardless of the fact that the hobbyist sees/notes no other changes in the fish.
[Some references spell the word m-e-l-a-n-i-n-i-z-a-t-i-o-n. I put the word melaninization and malaninization and malanization here for those searching for that spelling.]
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