Yes, that looks like fin rot. Do daily 75% water changes for 2 weeks. Add 1 tablespoon of aquarium salt ( not table salt) for every 5 gallons of water. Each time you do a water change, add that much of the original dose of salt back into water. Example: 50% water change = 50% of original salt doseage back in.
Is this a fin rot happening?
Hi and welcome to the forum
How long has the tank been set up for?
How often do you do water changes and how much water do you change?
What sort of filter do you have?
How often and how do you clean the filter?
How often do you feed the fish?
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The fish is producing excess mucous on its tail and this is usually caused by poor water quality or something in the water that is stressing the fish. Fin rot is caused by the same thing.
Check your water quality for ammonia, nitrite, nitrate and pH. Post the results in numbers here.
Do a 75% water change and gravel clean the substrate every day for at least one week and preferably two weeks.
Make sure any new water is free of chlorine/ chloramine before it's added to the tank.
No medication, it does not need chemicals. They will only make this worse.
If your nitrate is 160ppm, then do a 75% water change and gravel clean the substrate every day for the next 2 weeks. High nitrates will stress and kill fish. You need the nitrates to be less than 20ppm.
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You can buy sponges for different brands of filter and put them in your filter with the pads/ cartridges. You can use scissors to cut them to fit. Keep the sponges and pads together for 2 months then throw the pads away and just use sponges.
Its a 40 gallon tank and I have just 2 in thereHow big is the tank?
What fish are in it?
You've mentioned a black moor and the photo is a red cap oranda (I think) - are they the only fish or are there more?
Yeah I think its mucous as well..It has more patches now..but ill change the water this afternoon..i dont have a heater as of nowIt might not be ich. If the water is bad, and it apparently has 160ppm of nitrate, the black moor will be producing heaps of excess mucous just like the fish in the picture. This can look like white spots or patches but is just mucous.
If the OP posts a picture of the black moor, we can check it for diseases.
You also have to be careful raising the temperature on goldfish tanks, especially if they are cold (less than 20C). If they are in warm water already it's less of an issue but if they are in cold water, then raising the temperature to 30C (86F) can kill the fish.