Black aro fins??

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David R

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MFK Member
Apr 26, 2005
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New Zealand
Since moving into my 2000L tank the black aro has been growing fairly steadily, from ~12" to 18-19" since July. One thing I've noticed is the strange growth of his fins, more so the dorsal, tail and anal fins. It is as if the rays have been growing faster than the membrane between them. The water is good (very low hardness and TDS, pH ~6.8-7, 26-7C, 0 ammonia and nitrite, <20ppm nitrate), and the finnage of the other fish, including Geophagus and angels, is fine. I was wondering if the membrane would "catch up" to the rays, if it were caused by a growth spurt, but it appears to be becoming more exaggerated. The fish appears healthy, eats well (shrimp and hikari sticks), and the other fins appear unaffected. Any suggestions???

September;



Yesterday;





 
Definetly not typical growth, looks like some sort of fin rot. Just odd that it doesn't seem to affect the rays.
 
Definetly not typical growth, looks like some sort of fin rot. Just odd that it doesn't seem to affect the rays.

or the other long-finned fish! I'm reluctant to treat it without having some idea of what is going on though. It doesn't seem to be affecting the other fins, and the membrane doesn't seem to be eroding any further, if anything the rays are just getting longer.
 
That does look strange...

Have you tried adding salt?? I think that could be a worth a shot and is generally a safe option when treating damaged fins.
 
I think good clean water and time should go back to normal, I noticed something simular with my black arrow but it didnt last as long as what your describing.

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you can buy salt at lowes for way cheaper. about 5 bucks for 50 pounds instead of 10 bucks for about pound. just make sure its the not iodized one.
 
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