Goldfish has black spots

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Aquarium Advice Newbie
Mar 30, 2022
Hello, I'm new here and am also new to being a fish owner. My little girl who is 4 years old, won a goldfish at our local fair, which died the very next day.
After I went and spent like $70 on it a nice home and we hoped to have him live in and be happy in but poor little guy did not make it.

My boss has goldfish in his pond. Large ones, that he was nice enough to give her one of,
in replacement of her previous fish from the fair, that sadly died. ?

We have the new fish in an aquarium and we were trying to get our levels correct and in doing so, I believe between the water he came in, from his pond and our clean water, just mixed terribly.

Again, I'm far from a fish expert nor am I in anyway, firmiliar with how to test for all these things.

Tbh I'm fish-owner/fish tank retarded but I have grown fond of our little addition and have been really trying to understand it all.
I hope to have this one survive so that I don't have to explain to my 4 year old another time the sad reality about life and death.

I began seeing black spots on our poor fish. Large ones too.. So, we took him out of the tank and put him in small bowl while we cleaned out his tank, replaced the water completely, cleaned all the rocks, all the little decorations and everything.

I got a new cartridge to put inside his filter, waited 24 hours and began the process again.

I'm worried for him.

Maybe he is just stressed from the change but I'm also worried for his spots on his body.

I'm afraid to give him anything that could harm him more bc I've read that that the spots could be due to ammonia burns and I'm just afraid that our complete ignorance to what temperatures are correct for him, what to do when our water is hard, what to do to correct pH balance and alkalinity may not be on the ideal levels and it seems like everything I buy and try does not seem to be helping or clearing up his tank and now with these spots, just make me feel terrible, like I'm doing the opposite of helping him and I certainly don't want to be hurting him.

I just reintroduced him into the tank we cleaned but the water, even after 24 hours, is still very cloudy.

I bought some stuff called rapid cure and I haven't added it to the water yet bc I just want to be sure that, this is the correct solution to his issues before putting anything in whatsoever other than the normal tank solutions.

I have attached pictures of our fish and his spots. You can see the water prior to us changing the water completely was very cloudy.

I also attached pics of the test strips from the water, after the water change and if anyone could help suggest or point me in the right direction as to if everything should clear up and if the rapid cure should be added, I would greatly appreciate it.

I also have ick clear but haven't added that either.

The only thing we've put in the water is the water care kit and pH down.


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Whats going on is the tank isnt cycled. Im going to post something about the nitrogen cycle and how to cycle a tank.

In brief fish produce ammonia, and your tank isnt established sufficiently to remove ammonia. Goldfish are very messy fish, and produce a lot of ammonia. On top of that you are trying to keep what sounds like adult goldfish, so compared to a baby goldfish that's even more ammonia. On top of that im guessing a $70 aquarium isnt going to be big enough for a goldfish and isnt going to have enough filtration so that ammonia doesnt have enough water to dilute it out. On top of that those test strips dont test for ammonia so you have no idea how bad a situation you are in.

Can you confirm how big a tank you have and what filtration you have?

Can you confirm roughly how big that goldfish is?

In the short term, change 50% of the water twice a day until we can get a clearer picture of what you have.

Edit. On thinking further, can your friend take the fish back to their pond and we can start over from scratch?
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The nitrogen cycle is the natural processes that go on in your tank that convert ammonia into less harmful substances.

Ammonia gets into your tank through various pathways. Fish waste, decaying uneaten food, and dead, decaying plants are common ammonia sources in an aquarium. Its also possible your tap water is an ammonia source. Chloramine is a common water treatment and when treated with most water conditioners the bond in the chloramine breaks and releases ammonia into the water.

Ammonia can be toxic to fish, depending on how much there is, and what the pH and temperature of your tank water is.

The first stage of the nitrogen cycle is the removal of ammonia. If you have real plants in your tank some of this ammonia will be absorbed as part of their natural growth. Generally though ammonia is consumed by denitrifying bacteria that lives mostly on your filter media. These bacteria consume the ammonia and produce nitrite. Unfortunately nitrite is pretty much as toxic to fish as ammonia.

The second stage of the nitrogen cycle is the removal of nitrite. A different denitrifying bacteria will consume the nitrite and produce nitrate. Nitrate is much less harmful than ammonia and nitrite, and for most aquariums the nitrogen cycle ends there. Excess nitrate is removed through your regular water changes.

A further stage of the nitrogen cycle can also happen, but its difficult to remove all the nitrate from a typical freshwater aquarium. Plants will absorb some nitrate in a similar manner to how it absorbs ammonia to grow. There are also nitrifying bacteria that consumes nitrate and gives off nitrogen gas which will simply offgas from your aquarium. This nitrifying bacteria is difficult to grow in freshwater aquarium.

“Cycling” a tank is the process you go through to grow denitrifying bacteria in your aquarium to consume ammonia and nitrite. You are said to be “cycled” when you have enough bacteria to consume all the ammonia and nitrite that your tank produces and turns all of it into nitrate. If you test the water of a cycled tank you should see 0 ammonia and nitrite and some nitrate.
To cycle a tank you need to grow denitrifying bacteria to consume ammonia and nitrite that your tank produces. The bacteria needs an ammonia source to grow colonies sufficient in size to consume all the ammonia and resultant nitrite and turn it into nitrate which typically you remove through your regular water changes.

A fish in cycle uses fish waste as an ammonia source and regular water changes are undertaken to ensure that water parameters are maintained at relatively non toxic levels.

Set up your tank. Make sure everything is running smoothly. Make sure you have used a water conditioner product with any tap water you have put in your tank. Seachem Prime is a water conditioner that will also detoxify some ammonia for a day or two, so is a good choice for a water conditioner while cycling a tank with fish.

You should have a test kit. Preferably a liquid test kit. It should test for ammonia, nitrite, and nitrate.

In ideal circumstances you should be starting a fishless cycle with a low bioload (number of fish). 1 small fish per 10 gallons/40 litres is a good number of fish, but this can be tweaked a little for fish that are social and don’t do well on their own. Ideally a hardy type of fish. You may have fully stocked (or overstocked) your tank before you knew about cycling. In these circumstances, if its not possible to return fish, you will have to make the best of it.

If you haven’t already done so, add your fish. Acclimate them to the water in your tank before doing so.

Feed lightly to start with. Daily as much as is eaten in 2 minutes, or as much as is eaten in 3 minutes every 2 days. You can increase to full feedings if you are confident your parameters aren’t getting too elevated too quickly and water changes don’t become a daily thing.

Start to regularly test the water for ammonia and nitrite. At least daily. Depending on your bioload you could start to see ammonia quite quickly. Nitrite will likely take a little longer to appear.

Your target should be to keep ammonia + nitrite combined no higher than 0.5ppm by changing water whenever your water parameters exceed this target. 0.5ppm combined is a level of waste that is sufficient for your cycle to establish but relatively safe for your fish.

If you see 0.5ppm ammonia and 0.0ppm nitrite (0.5ppm combined) then leave things be. If you see 0.5ppm ammonia and 0.25ppm nitrite (0.75ppm combined) then change 1/3 of the water. If you see 0.25ppm ammonia and 0.75ppm nitrite (1.0ppm combined) then change 1/2 the water. If water parameters get worse than these levels it may require multiple daily 50% water changes to maintain safe water conditions. This is more likely to happen with a fully stocked tank.

Remember to add water conditioner whenever you put tap water in the tank.

Over time the frequency of water changes and amount you need to change to maintain your ammonia + nitrite combined target will reduce. You can also start testing for nitrate and should see this rising. If you are finding the ammonia and nitrite in your tests are consistently low, and you aren’t already fully stocked, you can add a few more fish. It may take a few weeks to get to this point.

Once you add a few more fish, continue to regularly test the water and continue to change water if you exceed the 0.5ppm combined ammonia + nitrite target. With added bioload the frequency of water changes and amount you need to change may increase again until your cycle has caught up. Again once you are consistently seeing low ammonia and nitrite you can add some more fish. Rinse and repeat with testing, water changes, and adding fish when safe to do so until you are fully stocked.

You can then cut back on water changes to control nitrate only. Typically you want to keep nitrate no higher than 40ppm, but I would recommend changing some water every 2 weeks even if your water test says you don’t need to.

A fish in cycle from an empty tank to fully stocked can take several months.

A good way to speed up this process would be to put a small amount of filter media from an established filter into your filter, or get a sponge from an established filter and squeeze it into your tank water. Perhaps you have a friend who keeps fish who could let you have some? This will seed your filter with the bacteria you are trying to grow and speed up the process.

Another option is bottled bacteria like Dr Tims One + Only or Tetra Safestart. These products wont instantly cycle a tank as they claim but in a similar manner to adding established filter media they can seed your filter with the bacteria you are trying to grow to establish your cycle. These products are hit and miss as to whether they work at all, but are an option if established filter media isnt obtainable and may speed up the process from several months to several weeks.
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