Can anyone identify this skin issue?

[Truus]

This is the picture that did not upload in my earlier post.  Can anyone identify this skin issue?

[Colu]

What are your water parameters and how long has it had this skin issue

[Truus]

On 9/18/2022 at 5:53 PM, Colu said:

What are your water parameters and how long has it had this skin issue

Water parameters are fine:  Ammonia is 0.25, Nitrite 0.0, Nitrate somewhere between 5.0 and 10.0, pH 7.2, and water temp is around 80F.

  I have not done a water change for a month now but the water is crystal clear.  I have a planted community tank that I started almost 3 months ago (but the filter, driftwood, rocks and bio-rings had been cycling for 2 months prior to that). The tanks is 55 gallon.  I am a newbie and my goal is to do minimal water-changes (taking Cory's advice)

This was the biggest and most dominant minnow in the tank. A noticed about a week ago that he became less aggressive, not parading around and chasing other fish.  It is just yesterday that I noticed the blotch.

About 3 weeks ago an angelfish died (it might have been fin-rot but he (most likely) was also harassed by the dominant angelfish) and a few days later another one was floating.  I then immediately did a 5 day course of antibiotics (erythromycin) and the angelfish bounced back right away.  She is doing fine now.  I have 3 angelfish and about 25 other fish from neon tetra's (smallest) to minnows (largest) and have no other fish die in the last weeks.

New in the hobby anxiety

Truus

 

 

[eatyourpeas]

On 9/19/2022 at 8:53 AM, Truus said:

Water parameters are fine:  Ammonia is 0.25, Nitrite 0.0, Nitrate somewhere between 5.0 and 10.0, pH 7.2, and water temp is around 80F.

Your water parameters are not fine.

Ammonia needs to be 0, and if you have minnows, the water temperature is a bit too warm for them.

Crystal clear water is not necessarily a sign of a healthy environment for fish.

It would be great to identify the source of ammonia. Have you had a fish die that you could not find?

[Colu]

That could be tissue damage caused by the ammonia that has developed a secondary bacteria infection I would recommend doing 50 % daily water changes and add a double dose of prime till your ammonia constantly stays at zero what I would do is quarantine and do a course of maracyn in food feeding a small amount twice a day for 7 days and add some aquarium salt 1 table for 3 gallons the salt will aid Gill function and add essential electrolytes and add an extra air stone