Black Spots On Fish

Try nail art brushes. They have various tools to put designs on fingernails. These include dotting tools and very fine brushes. You can get them on Amazon cheap.

 

Get some small vine charcoal sharpen and go to town on dots

 

Just airbrush them

 

https://www.winsornewton.com/na/graphic-art/graphic-markers/pigment-marker/

 

Also alcohol markers
Many differnt ways
Depends on how sharp a edge you want on lines and dots

 

https://www.winsornewton.com/na/graphic-art/fineliners/#product-info-features

They have the ink fineliners too.

 

Colors on a fish can come from many differnt mediums
In fact I paint my own eyes, after laying down my powders I use cigar ashes on my salmonoids for the background colors

 

Roflmao it’s been said time after crime that using sharpie pens do exactly that. Man so sorry to hear this but it’s why we use airbrush’s but wait there’s still more help if your not good at the airbrush.
Their are charcoal sticks, water color pencil, powder and paint pens.
Throw those sharpies away and get a good quality one at an art store. A company called pigma will carry pens that will work. Remember this using any kind of pens etc can make your spots very hard looking and unnatural. Charcoals can be softened up by using a small paint brush. This will get you on a better track

 

I've been looking into panpastels... Anyone have any thoughts?

 

What type of airbrush?
Harbor Freight (believe it or not) has one that will do some fairly fine lines/spots, down to about 1/16th"...if you have proper pressure setting, paint/thinner ratio and excellent trigger control. It's all of about $20. (it's the one with the blue handle...the one with red handle will give 1/4" at best). INITIALLY, they're as good as anything else I've used...but at $20...they don't have the longevity.

Micron pens will stay black under gloss coats. They're available at Michael's, have also found at Walmart, Staples, etc. Various sizes, down to .005. I started using em years ago...still black, 20 years later!
(I used them on enamel paints, with lacquer clears...no adverse reactions. Can't speak on them with acrylics)

 

I use them all the time
But not for fine lines
They are great

 

They work great on turkey heads. They should work on fish, I would think. I use workable fixatif to set them between coats. Matuska has on line videos of them using pan pastels on a variety of mediums.

 

I like using charcoal sticks to do my markings on my crappie diffused with a small fan brush. I have some of the Micron pens in the .01 and .005 sizes that I do pen and ink drawings with. May have to give them a try.