Ammonia & Nitrite Spikes: When to Worry (and When Not To)

Ammonia and nitrite naturally occur as byproducts of fish waste, uneaten food, and decaying plants. They aren’t always bad.

But when their level spikes, that's when it becomes a problem. High levels of ammonia and nitrite are harmful to fish.

However, with the right information, you can learn to spot the danger signs and keep your tank in the safe zone.

In this post, we'll dive into the ideal levels for a thriving aquarium ecosystem. I'll share which species are most vulnerable and give you tips to maintain that delicate balance.

Understanding Spikes vs Normal Levels

Let's break down what's happening in your tank and why these spikes occur:

The nitrogen cycle is the backbone of a healthy aquarium. Fish poop and uneaten food break down into ammonia. Bacteria then convert this ammonia into nitrite. Finally, different bacteria transform nitrite into nitrate. This process keeps your fish tank balanced.

A "spike" happens when ammonia or nitrite levels suddenly jump up. But not all spikes are created equal.

For ammonia, aim for 0 ppm (parts per million) in most tanks. Sensitive fish like Neon Tetras can't handle any ammonia. Tougher fish might tolerate up to 0.25 ppm, but don’t let it get that high in your tank.

Nitrite is similar. Ideally, you want 0 ppm. Some aquarium plants can use small amounts of nitrite, but the fish don't like it at all.

New tanks often have small spikes as the nitrogen cycle gets established. This is normal and usually settles down after a few weeks.

In mature tanks, sudden spikes often mean something's off—maybe overfeeding or a dead fish hidden in the plants.

Zero ammonia and nitrites mean bacteria are converting them efficiently into less harmful substances. A healthy, cycled tank ensures this.

The key to all this is regular testing. Check your tanks weekly, even after years of keeping fish. It helps catch problems early.

When to Worry About Spikes

Sometimes, ammonia and nitrite spikes can spell trouble. Here's when you should pay attention and take action:

Sudden increase in fish load

Adding too many fish at once is a recipe for disaster. For example, adding a school of 40 Tetras to a 20-gallon community tank would be a big mistake.

Sensitive species like these can't handle the sudden increase in waste. You could shock the system and overwhelm those beneficial bacteria that keep your tank cycled. A crash is imminent. 

Fish Death and Leftovers

Dead fish or leftover food are ammonia factories. Always do a head count during feeding time. If someone's missing, search the tank thoroughly.

Uneaten food should get scooped out after five minutes. Don't let it sit on the substrate (unless you have bottom feeders that are actively munching)

Insufficient or Inadequate Filtration

An undersized filter won’t be able to keep up with fish waste. If it's not powerful enough or clogged, ammonia and nitrite levels can rise.

Using New Filter Media

New filter media lacks good bacteria.

You'll often see hobbyists looking to trade or buy used filter media from other fishkeepers. Those used filter sponges, balls or plastic pieces are a goldmine of great bacteria that handle ammonia.

Seasoned hobbyists know not to replace those hang-on-back filter cartriges, but in fact, simply rinse debris off and slot it back in. This keeps some beneficial bacteria around to handle the bioload.

Watch your fish & inverts closely

Here are a few red flags to watch out for:

• Rapid breathing
• Gasping at the surface
• Loss of appetite
• Snails gathering right at the water's surface

If you spot these signs, test your water immediately. Quick action can prevent a full-blown crisis in your aquarium.

When Not to Panic About Spikes

Take heart. Not every spike means your fish are in danger. New tanks often have small ammonia and nitrite fluctuations. It's just part of the cycling process. Your tank is building up good bacteria. Give it time.

If you notice a tiny spike after a water change, that's a mini-cycle. It happens when you add new fish, too. Nothing to lose sleep over.

Regular water changes keep ammonia and nitrite in check. Do 20-30% changes weekly in your community tank. 

Don't forget about plants; they love to snack on nitrates. It's not a coincidence that heavily planted tanks rarely have nitrate issues.

The prevailing opinion is that they can't replace water changes entirely, but CAN drastically increase the time between them.

Keep testing, but don't stress over every little change. Your aquarium is a living ecosystem. Small ups and downs are normal and even healthy.

Considering Fish and Plants

Different fish have different tolerances.

For example, most Tetras and Corydoras get stressed at the slightest hint of ammonia. On the other hand, some hardy fish, like goldfish, mollies, and White Clouds, can tolerate very low levels of ammonia or nitrites (about 0.25 ppm) for a short time.

However, it's not ideal and can still be stressful or even harmful to their health in the long run.

Again, plants are great helpers in managing water quality. They love nitrates.

Quick-growers like Water sprite, Hornwort, and Duckweed are nitrate-eating champions. But don't rely on plants alone to keep ammonia and nitrite in check.

They're more like a helpful bonus than a complete solution.

Remember, a balanced tank with the right fish and plants makes for happy aquatic pets and an easier job for you.

Takeaway

Understanding ammonia and nitrite spikes is key to successful fishkeeping. With regular testing, proper maintenance, and a bit of plant help, you can keep your aquatic friends healthy and thriving in their underwater home.