Skip to content
Home » 10 Things You Should Never Put In Your Fish Tank

10 Things You Should Never Put In Your Fish Tank

If you’re a fish lover, you know that having a fish tank in your home is the next best thing to owning a pet fish. Not only do they provide hours of entertainment, but they can also help to brighten up any room in your home.

However, before you go out and buy your very own fish tank, there are some things you should keep in mind. In this blog post, we’ll discuss 10 things you should never put in your fish tank. So if you’re thinking of adding a fish tank to your home décor, be sure to read on!


You’ve probably seen those cool fish tanks made of plastic. And you might be tempted to put one in your fish tank. But plastic can be harmful to your fish. Plastic can leach toxins into the water and harm your fish. In addition, plastic can also trap and retain heat, making it difficult for your fish to stay cool.

toys in fish tank

Here’s what you need to know about the dangers of plastic in your fish tank.

Plastic is made from various synthetic chemicals, including some known to be toxic to humans and animals.

When plastic is exposed to water, it can release these toxins into the water, where fish can absorb them. In addition, plastic can also leach other harmful chemicals, such as BPA, into the water. These chemicals can disrupt hormone function and cause other health problems in fish.

So it’s best to avoid it altogether. Plenty of other materials can be used to make your fish tank, so there’s no need to use plastic. Your fish will thank you for it!


Another thing that you should never put in your fish tank is chemicals of any kind. Chemicals like bleach, ammonia, and other cleaning products can harm your fish, causing them to get sick or even die.

Instead of using harsh chemical cleaners, it’s best to opt for more natural alternatives. For example, you can clean your fish tank with mild soap and water or use a natural cleaning product specifically designed for aquariums. Researching and reading the labels of any cleaning products you plan to use in your fish tank is essential.

Be careful with the lighting.

You may be tempted to add a few colorful lights or even a spotlight to your fish tank, but this can pose a risk to your fish. In particular, bright lights can expose your fish to harmful UV rays and increase their risk of developing skin cancer or other health problems. Light also can cause stress and disorientation, and it can promote the growth of algae.

To protect your fish from the dangers of lighting, it’s best to avoid using bright lights and opt for more subtle lighting instead. You may even want to consider using natural sunlight or moonlight, which is less harmful to fish and other aquatic animals.

If you must use a light, make sure to use one designed specifically for aquariums and not too bright. For example, fluorescent lamps contain small amounts of mercury, so it’s important to always store and dispose of them properly, or you risk releasing toxic mercury into the environment.

Your best lighting options for freshwater aquariums are LED lights, as these emit less heat and UV radiation than other types of lighting. So if you want to add some extra illumination to your fish tank, opt for a low-heat LED light specifically designed for aquarium use.

Live plants.

Most fish tanks have some kind of decoration, and many people add live plants to their fish tanks. However, while live plants can be beautiful and help to keep your fish tank clean, they can also cause problems if placed incorrectly or overfed by your fish.

If you add too many live plants or are not kept healthy, they can cause excess algae growth and dirty your fish tank.

To prevent problems with your live plants, it’s essential to do some research before adding them to your fish tank. Read up on the specific needs of each type of plant you are considering, and make sure that you have the right equipment, such as a proper lighting system, in place.

It’s also important to feed your live plants regularly and keep them healthy so they don’t start growing out of control and overtake other parts of your fish tank.

Sharp objects.

Another thing that you should never put in your fish tank is sharp or jagged objects. Sharp objects like toys, glass items, shells, rocks, and aquarium decorations can scratch or puncture the delicate scales of your fish. This can lead to infections, pain, and even death.

To avoid putting sharp objects in your fish tank, it’s best to use soft materials for decorations and toys. You can even opt for artificial decorations instead of real ones if you want to be extra careful. And when choosing aquarium gravel or other substrate materials, always ensure they are smooth and non-abrasive.

In addition to avoiding sharp objects, you should ensure that your aquarium is always covered to prevent fish from jumping out or other animals from falling in. If you notice any scratches or punctures on your fish’s scales, you must immediately take them to a vet for treatment and care. Overall, it’s important to be vigilant and do your best to keep your fish safe.


Copper is an essential trace mineral found in many different kinds of foods. It’s also a common material used in plumbing and electrical wiring. While copper is safe for humans, it can be toxic to fish. That’s why you should never put copper in your fish tank. Copper can cause liver damage, respiratory problems, and even death in fish.

If you have copper pipes or wires in your tank, cover them with something to prevent your fish from coming into contact with the metal. In addition, avoid using copper-based medications or treatments in your tank. Taking these precautions can help keep your fish safe and healthy.



Coral is a beautiful thing to look at. It can be very colorful and have different shapes. A lot of people see it, and they think that it would be cool to have it in their fish tank. However, this is not a good idea. Coral should never go in your fish tank.

The first reason is that coral is alive. It is not like a rock that you can just put in your tank and forget about it. Coral needs specific conditions to thrive, and the coral will die if you do not provide those conditions. When coral dies, it releases toxins into the water, which can kill your fish.

The second reason why you should not put coral in your fish tank is that it can damage the equipment in your tank. Coral is very abrasive; over time it will wear down pumps and filters. It can also scratch the glass of your tank, which will reduce its clarity and affect the appearance of your fish tank. So, while coral may be pretty to look at, it is best to admire it from afar and keep it out of your fish tank.

Anything that is painted.

If you’re considering adding a little bit of color to your fish tank, you might want to think twice. While paint can add a nice touch to any home décor, it can be toxic to fish. When choosing paint for your fish tank, select a product labeled as safe for aquariums. Some paints contain harmful chemicals like lead that can leach into the water and poison your fish.

In addition, many paints are not designed to withstand the constant stretching and flexing that happens in an aquarium. Over time, the paint can delaminate and release toxins into the water. For the safety of your fish, it’s best to stick with uncolored glass or acrylic when it comes to your aquarium.

Too much food.

While it might seem harmless to add a little extra food to your fish tank when you’re already feeding them, there are a few reasons why this is a bad idea.

  • Uneaten food can quickly foul the water, making it dirty and contributing to the growth of harmful bacteria.
  • Leftover food can decompose in the tank and release toxins that can harm your fish.
  • Excess food can cause an algae bloom, choking your fish and making the tank difficult to maintain.

So next time you’re tempted to overfeed your fish, remember that it’s best to err on the side of caution. Your fish will be just as happy with a smaller portion of food, and your tank will be much easier to keep clean.

Dirty hands.

So, you’ve decided to start a fish tank. Congratulations! Fishkeeping can be a very rewarding hobby. But before you go out and buy your first fish, there’s something you should know: never put dirty hands in your fish tank. That might sound like common sense, but you’d be surprised how many people make this mistake. After all, it’s just water, right? Wrong.

Fish are extremely sensitive to environmental changes, and adding dirty hands to the equation can be disastrous. For one thing, the chemicals on your hands can throw off the delicate chemical balance in the water, causing all sorts of problems for the fish. Additionally, your hands can introduce all sorts of bacteria and other contaminants into the water, making the fish sick. 

So before you reach into the tank, make sure your hands are clean. It’s just a simple precaution that can help keep your fish healthy and happy.


When adding something new to your fish tank, it’s important to think carefully about any possible dangers. Whether you are adding live plants, lighting, or other decorations, make sure to do your research and talk to an expert to make the best decisions for your fish. By being mindful of the potential risks and taking steps to mitigate those risks, you can help keep your freshwater aquarium clean and healthy.