Help ID black spot on Melanurus

[rbkl]

Hi, my Melanurus has developped a dark/black mark behind it's fins. He has the mark on both side same emplacement. I am sure he didn't have it when I received it 6 months back. I spotted this new mark about 1.5 month ago and since he is almost not eating (live, frozen, dry, garlic, ...). He lost quite some weight and I fear it will die. Checked parameters are spot on since weeks but I had excessive PO4 at some point (0.9). One clown fish already died after not eating for a while.
Any idea if I can use any preventive treatment?

 

[smitten with ocean life]

#fishmedics

 

[Jay Hemdal Verified Community Expert]

Hi, my Melanurus has developped a dark/black mark behind it's fins. He has the mark on both side same emplacement. I am sure he didn't have it when I received it 6 months back. I spotted this new mark about 1.5 month ago and since he is almost not eating (live, frozen, dry, garlic, ...). He lost quite some weight and I fear it will die. Checked parameters are spot on since weeks but I had excessive PO4 at some point (0.9). One clown fish already died after not eating for a while.
Any idea if I can use any preventive treatment?

I’ve seen that coloration before, I’m not sure it is a disease symptom. Here is a picture off the Internet:

The not eating enough food is unrelated. What foods do you feed it? What does it do when it encounters food?

 

[rbkl]

I am feeding frozen Mysis and Artemia which it uses to eat fairly well. Since it stopped I tried with live artemias, many different high quality dry food with no success. It does swim all around at feeding time and inspect every single piece of food, but don't eat any. I tried additives such as garlic on the food as well but no effect on the Melanurus

 

[Jay Hemdal Verified Community Expert]

I am feeding frozen Mysis and Artemia which it uses to eat fairly well. Since it stopped I tried with live artemias, many different high quality dry food with no success. It does swim all around at feeding time and inspect every single piece of food, but don't eat any. I tried additives such as garlic on the food as well but no effect on the Melanurus

O.K., the inspecting of the food but not eating is a clear symptom; when a fish is very sick, they lose the urge to eat and just ignore food. However, your fish still has the urge to feed (seen by inspecting food) but it cannot feed. That is very often caused by some mechanical blockage in its throat. These blockages are commonly from swallowing a bit of gravel, but can also be caused by the growth of a tumor. Sorry, but there really isn't any treatment for either case.

 

[rbkl]

I was thinking about an injury but hoping for a worm that could be cured with medicine as well. Couldn't that be the case?

 

[Jay Hemdal Verified Community Expert]

I was thinking about an injury but hoping for a worm that could be cured with medicine as well. Couldn't that be the case?

No - internal parasites don't cause a fish to stop eating, if anything, they increase a fish's appetite as the fish tries to make up for the food calories stolen by the parasites.