Aquarium with fishes

Fish Tank Problems: 10 Disasters & How to Prevent Them

Besides being enjoyable to watch, keeping a home aquarium can provide pet education and stress relief…but disaster can quickly strike. Having your fish die due to mysterious fish tank problems can turn a hobby that once brought you joy into a huge source of distress.

Here are 10 fish tank disasters you might encounter, and how to avoid them. 

10 Common Fish Tank Problems 

Some common fish tank disasters include: 

  • Not acclimating new fish to the tank
  • Overfeeding
  • Impulse buying
  • Improper use of medication
  • Cloudy water
  • Inadequate filtration
  • Improper tank size
  • Overcrowding
  • Not letting the tank cycle
  • Not doing water changes

1. Not Acclimating New Arrivals 

When I was younger, I purchased my first fish for my newly established aquarium. I eagerly released them into their new home. To my shock, they died soon after. I had committed a common offense among beginning aquarists: failing to acclimate my fish.

Fish cannot tolerate sudden changes in water quality. The fish you purchase are placed in bags containing their original water, which will likely differ from the water in your tank. This sudden change in temperature and pH can lead to a quick death if you don’t acclimate them.

What to do about it

1. Turn off the aquarium light and dim the lights in the room. Doing this will help reduce stress in your fish.

2. Place the bag containing your fish in the aquarium and allow it to float for 15 minutes.  This will allow the temperature of the bag’s water to equalize with the tank water.

3. Carefully open the bag without letting any water escape.

4. Using a ½ cup measuring cup, pour water from the tank into the bag and wait 15 minutes.

5. Use a net to remove the fish from the bag and place it in the tank. Do not allow water from the bag to mix with the tank, as it may introduce diseases.

6. Leave the lights off for a few hours to allow your new fish to adjust.

🐠Read our full step-by-step guide to acclimating a new fish 

2. Overfeeding

Overfeeding is another common cause of fish death. Uneaten fish food will cause the water’s nitrates and ammonia levels to increase, which are toxic to fish.

What to do about it

Feed your fish once daily and only give them an amount they can eat in two minutes. If there’s any uneaten food remaining after two minutes, remove it from the tank.

3. Impulse Buying

While it’s tempting to purchase a fish because you think it would look good in your tank,  I highly recommend that you don’t make that mistake. You may be purchasing a fish with care requirements you cannot meet or who makes for a terrible tank mate for your current fish.

Thinking back to my first aquarium, I made the mistake of adding a betta to my community tank. In horror, I watched as it attacked my other fish. 

What to do about it

I recommend that you prepare yourself to avoid this kind of disaster. You can do that by doing your research before you purchase any fish to find out what species are compatible with other species. 

🐠Do you have a neon tetra or betta fish? Learn which fish make the best neon tetra tank mates and betta fish tank mates.

4. Improper Use of Medication

There are medications for tropical fish that contain toxic ingredients. When not used as directed, medication can kill your fish. These ingredients include:

  • Formaldehyde, aka formalin (commonly found in ich medication).
  • Chloramines
  • Glutaraldehyde (Can kill even when given at recommended doses).
  • Copper (is particularly toxic in soft water (less than GH). 
  • Glutaraldehyde, aka “Liquid carbon.” 

What to do about it

First, you need to properly diagnose the disease you’re attempting to treat, before jumping to medication. If you’re unsure, talk to a vet or with knowledgeable staff at your tropical fish store. Advise them of what’s happening with your fish and let them know the symptoms you’re seeing. Find out if the tank should be medicated and what medication they would recommend.

As well, I strongly recommend that you use a quarantine tank whenever possible to prevent the disease from spreading.

Here are a few helpful guides to help you diagnose diseases:

5. Cloudy Water

Cloudy water often has a grayish or whitish tint to it. It may be a sign of a problem with your tank if you see it. The most common causes of cloudy water are:

  • Gravel that has not been properly washed.
  • Your tap water has quality issues.
  • You have a bacterial bloom.

What to do about it

If the problem is that the gravel wasn’t properly washed, the water may clear up by itself. Just give it a few days. If the water doesn’t clear by then, do a partial water change. In extreme cases, you may have to drain the tank and wash the gravel again.

Quality issues with tap water may include high pH or phosphate levels, or there may be heavy metals in the water. You can resolve this by treating the tank with a water conditioner. Do a water change and add the water conditioner to the new water.

Bacterial blooms may be caused by overfeeding or by having too much decaying plant matter in the tank. Use a water testing kit to check the levels of nitrites, ammonia, and nitrates. If needed, do a water change and add a water conditioner

6. Not Doing Water changes

Partial water changes should be done weekly to maintain the water quality. Even though the water may look clear, there will be a buildup of waste. Waste increases nitrates and phosphate, and the fish are sensitive to these changes in water quality. As well, water changes done incorrectly can kill your fish, so it’s important to not only do a water change but do it correctly.

What to do about it

Only replace 10% -15% of the water weekly when doing a partial water change. If the aquarium is heavily stocked with fish, do a 20-25% water change weekly.  

How Do I Know if the Water in My Fish Tank Is Bad?

You can get water test kits from your tropical fish store to test for:

  • pH
  • Ammonia, nitrates, and nitrites
  • Water hardness

7. Inadequate Filtration

Aquarium filters are rated for the water capacity they can handle. This rating will appear on the product’s packaging. You can create problems by buying a filter rated for a smaller tank capacity. Not providing adequate filtration can lead to water quality issues and sick, stressed fish. 

What to do about it

Buy a filter rated for an aquarium slightly larger than what you need. Doing this will ensure that you are getting adequate filtration.

8. Your Tank is Too Small

There’s a misconception about the size of starter aquariums. Most new fishkeepers think they should start with a small tank, as it’ll be easier to maintain. The truth is the smaller the aquarium, the more unstable it is, as it’s more difficult to maintain the water parameters. Larger tanks offer more leeway if anything goes wrong with the water quality.

What to do about it

If you’re a beginner, get a 20-gallon aquarium or larger. Start with the largest tank you can afford.

9. Overcrowding

Overcrowding the tank will increase waste, and raise the tank’s phosphate and nitrate levels. It also reduces oxygen levels and may increase aggression in your fish.

What to do about it

The standard rule is one inch of fish per gallon of water. So, if you have two fish that are three inches long, you will need at least a six-gallon tank.

10. Not Letting Your TankCycle

Cycling refers to creating a biological balance in the aquarium. New tanks need to establish bacteria growth, and for this to happen, they need ammonia and nitrates to feed on. If you introduce fish before the bacteria are established, they’ll die from toxic water.

What to do about it

It takes four to six weeks for a tank to cycle. You can speed up the process by purchasing live bacteria from your tropical fish store.

What Is New Fish Tank Syndrome?

New fish tank syndrome is a tank that has not been cycled. Avoid new tank syndrome by cycling the tank.

Follow Our Tips to Avoid These Fish Tank Disasters

This article is just a partial list of what can cause an aquarium disaster. Before embarking on your fishkeeping journey, you must research how to set up an aquarium and the fish species you plan to get. By doing your homework, you can avoid many of these fish tank problems.

We would enjoy reading your comments, and please share this article with your fishkeeping friends.

You can also create engaging videos and share them on social media. Start by showcasing common dos and don’ts in fishkeeping, emphasizing proper maintenance routines, water quality checks, and appropriate feeding practices. Share real-life scenarios or reenactments to highlight the consequences of neglecting these aspects, such as water contamination or overfeeding. Additionally, offers practical tips and solutions to prevent or address potential disasters. Finally, when sharing these videos on social media, make sure to use a video editor and compress videos to ensure quality and make them more engaging.

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