What is Ammonia and Why is it Dangerous?

For more detailed information on the nitrogen cycle, you can also check out our guide on Understanding the Nitrogen Cycle.

Now, here is where the problem hits. When your tank has too much ammonia and not enough of those helpful bacteria to deal with it, things start going south. Ammonia is pretty nasty for fish—imagine swimming in a pool full of bleach. It burns their gills and makes it tough for them to breathe. You will see them gasping for air, hovering at the surface like they are begging for a way out. It is not a pretty sight.

I remember the first time I saw a fish struggling with ammonia poisoning. It was heartbreaking. A couple of neon tetras just hanging at the top, moving slow, and their gills looked red and inflamed. I had no idea what was happening at the time, and let me tell you—it is not an experience I would wish on anyone. The good news is, once you know what is happening, you can fix it. Let us break it down.

Common Causes of a Sudden Ammonia Spike

So, you want to know why this ammonia mess even started, right? There is no single culprit. Let me tell you about the top reasons I have run into (and trust me, I have run into them all).

1. Overfeeding

If you are dealing with algae issues due to overfeeding, consider reading our post on How to Prevent and Remove Black Beard Algae.

Tip from Experience: Feed your fish less than you think they need. And if you are worried about getting the portions right, an automatic feeder like the Zacro Automatic Fish Feeder might be your best friend. This little gadget can help take the guesswork out of feeding, and it does not have a soft spot for cute begging fish.

2. New Tank Syndrome

Ah yes, the classic new tank syndrome. I have lost count of how many times I hear this phrase from new aquarists who call me in a panic. They set up their tank, everything looks good, and then boom—fish start dying left and right. The problem is, the tank did not have enough time to build up a population of beneficial bacteria before adding fish.

Let me tell you, I made this mistake with my first tank. I did not cycle it properly, and it turned into a ticking ammonia time bomb. Now, I always preach the importance of cycling. Give that tank 4-6 weeks to establish itself before adding any fish.

A Quick Tip: Use a bacterial supplement like Seachem Stability to help get your tank off on the right foot.

3. Dead Fish or Decaying Matter

Look, life in an aquarium can be brutal sometimes. Things die. And if a fish, shrimp, or plant dies without you noticing, it is going to rot in the tank and release ammonia. I have had a shrimp that I swear was playing hide-and-seek with me for days after it passed. I eventually found it wedged behind a rock, and by then, my ammonia levels were through the roof.

4. Filter Problems

Your filter is like the heart of your tank, and if it is not working right, the whole system falls apart. If the filter gets clogged or stops working properly, the waste stays in your tank. One time, I had a sponge filter that I forgot to clean for way too long, and the ammonia levels spiked before I knew it. Filters need to be checked and cleaned regularly—without being too aggressive, of course, since you do not want to kill off those precious bacteria.

5. Overcrowding the Tank

There is something called the “inch-per-gallon” rule that suggests one inch of fish per gallon of water. Well, let me tell you, it is not a perfect rule, but it gives you an idea. The more fish you have, the more waste they produce, and if you pack your tank like a clown car, no filter in the world is going to keep up. I learned that the hard way after thinking, “Just one more fish will not hurt.” Spoiler alert—it did hurt.

How to Identify an Ammonia Spike

Spotting an ammonia spike before it is too late is half the battle. I like to keep an eye on my fish for anything that seems “off.” Fish will tell you when something is wrong—you just need to know what to look for.

Signs of Ammonia Poisoning:

• Fish gasping at the water’s surface.
• Inflamed, red gills.
• Sluggish, lethargic behavior.
• Discoloration or unusual white patches on the skin.

Whenever you notice these symptoms, grab your test kit. I always keep my trusty API Freshwater Master Test Kit on hand for moments like these. I would recommend testing at least once a week, but if something seems off—test right away.

Immediate Steps to Take During an Ammonia Spike

So, you tested your water, and, surprise, surprise, there is an ammonia problem. Time to roll up your sleeves and fix it. Here is what you should do:

1. Perform a Water Change

For water conditioning, you may want to consider using Seachem Prime, which is perfect for detoxifying ammonia and other harmful substances.

2. Add an Ammonia Detoxifier

I will be honest—ammonia detoxifiers are not magic, but they are helpful. They make ammonia less toxic temporarily, giving you time to sort things out. Again, Seachem Prime is a solid option, and it is saved my fish more than once.

3. Remove Decaying Matter

Look around—any uneaten food, rotting plants, or dead critters need to go. I have done more than one emergency clean-out at midnight after noticing a problem.

4. Check and Clean Your Filter

If you are looking for a reliable filter for your shrimp tank, check out our recommendations in Best Filters for a Shrimp Tank.

Preventing Future Ammonia Spikes

Once you get through an ammonia crisis, you will want to do everything you can to keep it from happening again. Prevention is always easier than emergency intervention.

1. Consistent Tank Maintenance

Weekly water changes and cleaning are your best bet. I like to do 20-30% water changes each week, siphon out any debris, and wipe down the glass.

2. Regular Water Testing

Testing is the only way to know if something is going sideways before it becomes a big issue. Testing weekly keeps things on track and helps you catch any ammonia creeping up.

3. Feed Smart

Resist the urge to overfeed! Fish will always act hungry, but they do not need as much food as you think. Stick to feeding small amounts that they can eat in a couple of minutes.

Advanced Tips for Experienced Aquarists

For those of you who have been around the block a few times, here are some additional tips to help keep your tanks healthy and ammonia-free:

1. Boost Biological Filtration

Consider adding more biological media to your filter. The more surface area you have for bacteria, the better. Filters like the AquaClear Fish Tank Filter are great for customization.

2. Seeding New Tanks with Mature Media

Whenever I set up a new tank, I always grab some filter media from an established tank. It is like giving the new tank a head start with a ready-made population of bacteria. This tip has saved me a lot of time and headaches over the years.

3. Keeping an Eye on Your Bio-Load

Regularly assess the number of fish and other critters in your tank. As fish grow, they produce more waste, so what worked a year ago might not work anymore. Stay aware of the balance between your tank’s inhabitants and its ability to handle waste.

Ammonia spikes are no joke, but they do not have to be a death sentence for your aquarium. I have been through my fair share of ammonia scares, and I am here to tell you that you can get through it too. The trick is staying vigilant—watch your fish, keep up with maintenance, and test your water regularly.

Aquarium keeping is not always smooth sailing, but it is a journey worth taking. There will be mistakes, sure, but that is how we learn and get better. And hey, if you have had your own experience with ammonia spikes, I would love to hear about it. Share your story in the comments below, and maybe together, we can help make these unexpected spikes a thing of the past.

And do not forget—if you need more help with your aquarium or want some product recommendations, you can check out other posts on the site. I am always here to help you and your critters thrive!