New Contributor

Red Spots Appeared on my Goldfish

Ever since we got a pleco fish, red spots started to appear on all the goldfishes. It got worse as the days went by and they started to even get lethargic. Then I saw the pleco fish swim up to one of the resting goldfish and start sucking on it till the goldfish swam away. We quickly put the pleco fish into another tank, and we also changed the water. Red spots have never appeared and we had a pleco fish with the other goldfish before. The goldfish are doing fine now, swimming around after we changed the water. But I just want to know what's going on. 

Community Representative

Re: Red Spots Appeared on my Goldfish

Hi IrishJane and welcome to our community. We'll touch base with our animal expert for more information.
Occasional Contributor

Re: Red Spots Appeared on my Goldfish

Red spots (broken blood vessels) mean high ammonia or nitrites in your water. Great move on putting the pleco into another tank, lessens the bio-load within the tank. (Lower bio-load = lower ammonia/nitrite/nitrate production)

Just keep your water changes consistent as goldfish produce a lot of waste.
Community Manager

Re: Red Spots Appeared on my Goldfish

Hi IrishJane. Our experts have a few more questions: 

What do the red spots look like?

Are they small and have they changed over time? If so, what do they look like now?

How large is your tank and how many fish (and species) do you have? Could they be fighting wounds?

What are you feeding the pleco?


Generally pleco fish are not considered aggressive, however if they are not fed the appropriate food, they may bite or suck on slow moving fish. If this is what you are seeing, keeping these two species in different tanks should resolve this issue. We generally do not recommend a pleco which thrive in tropical water be housed with gold fish who thrive in cold water.


We hope this helps!  And please keep us posted!

New Contributor

Re: Red Spots Appeared on my Goldfish

The red spots started as small, that they weren't really noticeable and a bit on the stomach and sides, but I thought ti just came from laying down a lot. After a day or two the spots started to get bigger and now it's all over their bodies and fins too that it looked like they were fighting. 

The fish tank is 55 gallons with currently 6 fish inside, the pleco already in another tank. I don't think it could be fighting wounds since the fish have never done that before. I feed the pleco an algae wafers.

Community Representative

Re: Red Spots Appeared on my Goldfish

Thank you so much for those answers, is there any streaking surrounding the spots on the fish? Can you send photos of the tank and a clear close up or two of the fish with red spots? 

 Our recommendation is 1" of gold fish per 5 gallons of water so depending on how large your gold fish are, you may be dealing with crowding or potential water quality concerns. Have you checked water parameters recently? If so what were they and on what date? 

   - If you do not test at home, your local Petco aquatic department would be happy to perform this testing for you. You will just need to bring in a small sample of water. 

 We always recommend a varied diet for your aquatic life, so you may want to consider adding other options to the current algae wafer diet. 

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