Creature on goldfish fin

Question
QUESTION: Hello. I have a 6 gallon tank with a filter and air stone. I bought two comet goldfish last saturday and yesterday i noticed that one of them got a mark on a pelvic ventral fin. It looked like a scale or something and today i noticed that it moved to dorsal fin! I had a good look and realised that it is a creature. It is flat round greyish and has a lot of legs! What can it be? Is it hurting my fish and how can i get rid of it?! I really appreciate your advise, thank you.

ANSWER: Hi Karolina,

First of all, each goldfish, even as babies, requires 10 gallons of water.  As adults, 3" to 5", at least 25 gallons each.  Please super filter.  Goldfish are very dirty fish.

Take the fish out of the tank.  Get some Marine Salt.  Add 2 dissolved teaspoons of marine salt into a bowl, (a gallon bowl, or 2tsps per gallon, to 3 tsps per gallon) and add the fish.  Soak him for 24 hours in the bowl.  The creature on him will die.  I'd like to see a photo of it.  Please send it.



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QUESTION: Hello again. After a careful research on the internet I found out that my gold fish has a fish lice(louse). As the pictures I found look exactly the same as the creature on my fish, they are hurting him and damaging his skin. I am going to get a bowl tomorrow and soke my goldfish in the salt solution. however do you know if i need to do anything with the tank? To give it a clean or should I get some sort of medication? I don't trust fish shops much as every time I go there they keep selling me expensive stuff that doesn't do much. By the way I am also looking into getting a much bigger tank as I got the small one just to learn the trade, the problem i've been having so far is keeping the fish alive.

Thank you for your help.

ANSWER: Hi,

I suspected it was a fish lice, but without looking, I could not be 100% certain.  I am glad you found it.  The salt solution will help.  Fish lice will breed in the main aquarium, FAST.

If you don't have any live plants, please treat the entire tank.  2 teaspoons of aquarium salt, dissolved thoroughly, per gallon.

In 3 days, you can begin draining and exchanging water so that you are replacing the saltwater with fresh.

Begin with half the tank in 3 days, draining 50%.  Replace with pure freshwater.

You can leave 1 teaspoon of salt per gallon in the tank (that's leaving the other 50%, replacing a teaspoon per gallon when you do your weekly water changes of 25%, as recommended) from here forward.  It's not going to hurt the goldfish.  They are able to deal with it.  Also, it prevents a ton of diseases, but if you don't increase the aquarium size, you will run into issues down the line with their health, because of water quality.  Just a head's up, early on, before the build-up of toxin hits them in a few months to a year/two.  Sometimes it takes time.  Sometimes it's very fast.

Fish lice are no laughing matter...worse, you must notify the store you bought him in.  Their own fish have it, and other people will be taking home fish lice.

Happy fish-keeping and have a great day...if you need any further help, please let me know.  I will do my best to assist you.

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QUESTION: Hello again, thank you for your help. Can I leave both fish in the tank while I'm treating it wih salt or should I take them out and put them in  a bowl for 3 days? Sorry to ask you so many questions.
thank you

Answer
I would treat the entire tank.

I would treat them together.

a few days after treatment begins, drain 50% of the water, replacing it with fresh water.

Water changes are necessary anyway...this will jumpstart that good habit.:)

Happy fish-keeping.