Goldfish w/black areas & specks on fins

[1fish2fish]

We have a 16x12ft backyard pond. We are still waiting for our pond maintenance crew to come so the pond has not yet been cleared for the coming season, but we did place the waterfall, pump, filter and aerator while we wait. When the pond thawed this spring, we thought this fish had passed over the winter as it was missing. A few weeks went by and one day we saw him swimming on the bottom of the pond in the muck. He was once white, but now looks blackened with some redness and what looks like bleeding at the base of the fins. The rest of the pond fish are all acting normal and look healthy. We removed him from the pond and have him in a 20g quarantine tank. I have the tank filtered and had been doing frequent (every 3 days) 25-50% water changes as I thought at first these were ammonia burns and swim bladder with the dark black areas and red gills, though the black fin specks were throwing me off.
I decided to treat with PraziPro and Maracyn 2 as I suspected possible bacterial infection/septicemia secondary to a fungal infection such as black smudge. He is acting much happier now and is able to swim off the bottom of the tank after about 4 days of the one treatment with Prazi and 6 of Maracyn2. He still looks awful though. We’ve been feeding him cooked pealed peas as well. His appetite was very poor up until a few days ago.
We did check water with the API test kit and its perfect both in the tank and the pond. The tank water looks murky as I just treated it with the antibiotic for the day, so apologies for the blurry photo.
We did have a Blue Heron visit our pond last year and take half our fish- this guy was one of the survivors. So I’m wondering if it started from a parasitic infection from the bird. We also have snails in the pond (which we’re hoping the pond crew will get rid of when they come).
Any help is much appreciated. Am I doing this right? We inherited this pond, so we’re still learning. As you can probably tell from my comments- I’ve learned more in the last month about fish health than I learned in the last 33 years of life. But honestly, if this fish can be saved, I’d be really happy as I’d like to prevent this sort of thing in the future.
First photo is from when I first removed him from the pond and he couldn’t get off his side, so I’m sure something with his swim bladder. Second is today (treated water), and he’s up and swimming about the tank and very active.

 

[j.w]

and welcome @1fish2fish
That fish looks like a Shubunkin type of goldfish and they can turn colors as they grow.

Shubunkins:

 

[mrsclem]

I agree that it looks like a shubukin so the black spots are just a color change. Don't see the red at base of fins but that maybe from the treatment. He doesn't appear bloated so not sure why the peas. How was he acting before you removed him?

 

[brokensword]

agree with the above advice. Goldfish are pretty tough but coming out of winter, there can be transition problems that can resemble issues. Especially if the fish is acting normal and has an appetite, I'd just watch and if all continues positively, put him back in the pond.

And though you didn't ask, most here don't ever promote 'cleaning crews' for their ponds. We tend to lean toward natural methods and balancing the system that way. There's no chems involved, no scrubbing of the beneficial biofilm on the pond's underwater surfaces, no start-up-again syndromes, very little algae problems, and generally, healthier fish. If you want to go further, search 'bog' here and read some of the threads to learn about the magic therein.

Hope this helps.

 

[1fish2fish]

thanks everyone for the advice- he does look like a shubunkin. The redness around the bases of his fins has drastically improved just in the last couple days. When we first took him out of the pond (the first picture, where he couldn’t get off his side), it wasn’t there but developed about a week after. At that time we just tried water changes, but he seemed to be getting worse instead of better. Since starting the prazipro and antibiotic he has improved and is actually now swimming around the tank, but still sinks to the bottom if he isn’t actively swimming. We did peas as I had read this can be helpful for the fish while swim bladder issues resolve. Last summer, we did notice he was bloated... I foolishly thought maybe that was just that he ate too much. In hindsight, I think he was ill already at that point. He no longer looks bloated, but he does sink.

The maintenance folks we have coming don’t use chemicals. The pond was left uncared for for about 2 years before we bought the house, so it is overgrown with weeds and cat tails and lillies and is very gross looking with a substantial amount of algae. It’s a miracle the water quality is good, but we also didn’t check the water until after we replaced the pond filters/equipment back in for the spring. We have a small place here that specializes in koi and goldfish ponds and they are coming to help clear out all the excess debris and get the pond looking nice and healthy again and to teach us what to do ourselves to maintain the pond so we can maintain it ourselves. I searched bog and this place we have coming has a pond outside their shop that looks very similar to these photos of bog filters, so I wonder if this is something they could help us initiate for our pond. I appreciate your feedback- I plan to ask them about this