The leading cause of death in aquariums worldwide is traced to one notorious killer: ammonia. Interestingly enough, disease isn’t as much of a predator of goldfish’s lives as ammonia. Because water quality plays such a huge roll in the health of goldfish, we are going to take a look at the importance of keeping it under control and “knowing your enemy,” so to speak. By understanding the nature of this ruthless assassin, you will be better able to keep your fish safe from its attack.
What is Ammonia?

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A chemical compound (scientifically NH3/NH+4) of nitrogen and hydrogen atoms, ammonia is extremely toxic to goldfish. It can enter your aquarium through tap water, rotting material such as plants or food and goldfish waste. Ammonia is the primary waste product of goldfish, with 25% excreted through their solid waste and 75% excreted through their gills.
You cannot see ammonia in the aquarium because it is colorless. A tank with murky water teeming with algae may be far safer than a sparkling clear tank for that very reason. Because it is invisible to the eye, detecting ammonia is only possible through water tests. A liquid test kit is very helpful in being able to tell if there is ammonia in your tank, and something that every goldfish owner must have on hand.
Ordinarily, ammonia leaves the goldfish’s bloodstream without any effort on part of the fish. The ammonia is then converted into safer forms via The Nitrogen Cycle. When ammonia is not properly converted for any reason, it lingers in the tank and prevents the goldfish from being able to get rid of any ammonia. The result is ammonia poisoning.
What are the Effects of Ammonia Poisoning?

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Ammonia causes a wide range of health issues to occur in goldfish. Symptoms of ammonia poisoning include:
- Gasping or hanging listlessly at the surface of the aquarium
- Streaks of blood in the tail and fins
- Clamped fins
- Sitting on the bottom of the tank
- Lethargy
- Wasting
- Difficulty breathing, repeated “yawning”
- Decreased appetite
- Increased mucus production
- Red flecks on skin (blood hemorrhaging)
What to Do for Ammonia Poisoning
You can see by the many symptoms of ammonia poisoning how it is often mistaken for disease. Treating a goldfish suffering from ammonia poisoning with medications intended to combat disease is usually deadly to the goldfish. Ammonia poisoning is common in tanks that have not been cycled and causes fish to undergo New Tank Syndrome.
Rather than run to the store to buy more chemicals to add to the unbalanced aquarium, it is recommended to do a large water change right away and continue doing them successively every day until the ammonia is no longer measurable. If your tank is not yet cycled and you have fish in the tank, you may be looking at repeated occurrences of ammonia poisoning until the cycle is complete and your fish may not make it.
Preventing Ammonia Poisoning
Because of the destructive and often deadly effect of ammonia, any trace of it in the water higher than 0 is unacceptable.
Ways you can prevent your goldfish from coming down with this terrible condition are:
- Cycling your goldfish tank first before getting fish
- Avoiding overfeeding your goldfish
- Doing regular weekly water changes of at least 50%
- Stocking your tank properly
- Testing the water on a regular basis
my fish died from this but wouldn’t live :S
That’s too bad, shelby 🙁
So the water changes are the only way or the best way to take care of ammonia? I’m having ammonia issues in my tank (I have a test thingy that just hangs in my tank on a suction cup) and I would like to save my feesh before they get sick. I was an idiot and didn’t know about cycling before I got my babies and don’t want them to suffer for it.
Water changes, Prime, fast-growing plants like hornwort are my 3 go-to’s.
Do you know how long ammonia burns take to treat?
They can take several weeks to heal.
Hi there, we have two small goldfish in our 10 gal tank, I know they are supposed to have a bigger tank but my fiancé insisted on starting smaller. I’ve been testing the water regularly and the first time I tested the water I was at 0.25 for ammonia and then the second time two days later I was at 0.5, I’ve been putting API stress/coat, and API quick start regulaly (almost everyday) I just tested my water again about a week after the last time and now my ammonia is at 1.0. Both my nitrite and nitrate have been at 0 every time I’ve tested… I’ve done 2 water changes, am I doing something wrong? Is there something else I should buy? One goldfish has the black spots, the other looks pristine. Now they are both kinda hovering the bottom of the tank and don’t have much of an appetite. I think part of the problem is my fiancé feeding them. I’ve caught him over feeding before or letting our toddlers feed them. Before they would swim around in their bubble wall and looked all happy but now not so much.
I don’t know how old your tank is, but if it is new, you might be dealing with new tank syndrome. If the tank is aged, your filtration may be inadequate and you can try adding more biological filtration surfaces, a mini sponge filter would be perfect.
First let me just say that you have by far the best resource for goldfish care. Anytime my goldfish gets sick or somethings wrong, I freak out because I have to go through all the forums and don’t even know if I can trust people. Your site is awesome. Thank you so much!
my eight-year-old black moor seems sick all the time (I avoid medications, but I always test the water and do water changes multiple times per week) nitrates were a little high but I thought I got it under control. I got another fish and after quarantining him, but him in the tank, and he immediately started acting off too. I’ve been going nuts trying to figure out what’s wrong. And after staring at my computer ready to pull my hair out all day, checking for signs of anything on the fish, i finally noticed a red streak on the older ones tail. Tested for ammonia again, and I think it’s been constant low levels of ammonia this whole time… so thank you for being an amazing resource. I don’t know what we would have done without you!
Thank you for your kind words Bliss ^_^ Glad to hear your fish was helped!
Hi, (get ready – story time!)
A while ago I got my goldfish, after setting up my tank and letting it \’run\’ for a week (I know i\’m so silly, I listened to the unassuming pet store employee!). It was a black moor and it seemed happy for almost a week after being purchased.
And THATS when my goldfish started doing weird things.
My father said that goldfish gulping and sliding along the glass was perfectly normal, (of course) I did not listen to him. I had no idea about what the cycle was, and when I found out, oh boy I was in trouble.
Fast-forward to now, and I have purchased another fish after cycling my tank. My black moor STILL gulps air after all of this chaos, and I have done EVERYTHING to see what the cause was: high ammonia, nitrites, nitrates, low oxygen levels, disease?, something else weird, but I found nothing that I could conclude that was the cause of my goldfish gulping. Nothing!
I then re-enacted going to the pet store and purchasing him, but I didn\’t remember anything wrong with him (I remember he looked really cute in the little bag he came in, just bouncing around).
I was freaking out because I thought that I was a bad goldfish owner and I was causing my little fish to suffer because of my mistakes.
That is how I found your website (I actually found it before I was a goldfish owner, but it has recently become really useful). I am wondering if ammonia, nitrites, or nitrate in high amounts damage (irrepaireably [is that even a word]) the gills?
I am really grateful to your website as EVERYTHING (not in any way an exaggeration) I have learnt about keeping goldfish, I have found in your AMAZING blog!! I owe you and your blog my goldfish\’s lives!
Thanks for the help. I REALLY appreciate it. Your blog AMAZING!
~Anonymous goldfish enthusiast
Poor water quality can fry the gills, but fish can recover in time if it isn’t too out of hand. Thanks for your kind words 🙂
Hi,
Just wondering, what would you classify as ‘out of hand’?
Too much exposure to high levels