Dangerous Things You Don’t Want In Fish Tank.

What Is Dangerous To Put In Your Fish Tank? Fishkeepup.com

As exciting as building and decorating your fish tank is, there are also many pitfalls that can undo your hard work. When I got my first fish tank a couple of years ago, I simply had no idea what to do or not to do, so I asked around and carried out some research.

What Is Dangerous To Put In Your Fish Tank? The short answer is that you need to avoid anything that will release toxins into the fish tank, all degradable and sharp object should be also avoided. In addition consumable objects and objects that may alter the chemical properties of the water, not use it. Stay away from objects that may trap your fish.

When looking out for dangerous things to avoid putting into your fish tank, it isn’t as straight forward as you might think. Read a bit further and you will understand the many variables that you need to consider before deciding not to include certain objects in your fish tank. 

Can I Put Plastic Toys In A Fish Tank?

Plastic toys generally just add to the aesthetics of your already pleasing fish tank. Logically, plastics aren’t degradable and should be safe for your fish tank. 

This might not work in all cases because when some plastics are left in water, they tend to release some chemicals into the water over time. These chemicals may or may not be harmful, but that’s not a risk we’re willing to take. 

To make sure a plastic toy is safe for your fish tank, make sure that the plastic is “food safe”. You will often see a triangle made up of three arrows on the label. This means that you can put it into your fish tank.

When plastic was designed for one-time use only, that is, disposable plastics, these should always be avoided as chemicals can leach into your fish tank if used for a prolonged time. 

Remember these plastics were not made for prolonged use. To be safe, only use plastics when you absolutely must. And when you do, make sure your plastics aren’t chipped or split.

Can I Put Fresh/Tap Water In My Fish Tank? 

Adding fresh water to your fish tank actually depends on what type of fish you’re dealing with. Freshwater fishes would need fresh water while sea fishes would need saltwater. 

A lot of people would typically prefer to simply add water from the faucet directly to their fish tank. This might not be a very good idea in most cases since it is rather difficult determining whether or not the water contains harmful chemicals that may harm the fish.

Before adding water to your fish tank, either for the first time or changing out “old” water, the safest approach would be to test the water source. The quality of the water means life or death for the fish.

Testing your water ensures that you do not place your fish in water that negatively impacts their wellbeing. Testing can be done using an aquarium test kit.

If after testing your water, you find that some parameters are off, there’s no need to panic. Since you now know what parameters to work on, you can simply walk into a nearby aquarium supplies shop to get one of many products that can help improve water quality.

A quick tip, however: You might want to choose a fish species that can survive and thrive living in the water of your specific parameters. This will reduce the stress of having to prepare water all the time.

If you already have a certain fish species in your fish tank, and your water parameters aren’t suitable for your fish, you can simply pre-treat your water before adding it to your fish tank.

To pre-treat water, you must first put water in a bucket clean bucket, and then condition the water according to the instructions on the conditioner bottle. 

Be sure to ask your fish breeder for the best conditioner for your fish.

How to ensure about tap water

What About Bottled Water In My Fish Tank?

Bottled water is ideal for human consumption. Note that bottled water was made for people. 

Also, not all bottled water has the same properties. In fact, there are three common types of bottled water:

Filtered water:

this water is just tap water that has been passed through various filters and maybe even charcoal.

Purified water:

this type of bottled water is gotten when tap water is passed through an RO/DI Reverse (Osmosis / Deionization) system. It can also be distilled water. The best option is  6 – stage reverse osmosis filter where the price starts from a little over 150 USD. Link will direct you to Amazon.


this type of bottled water tends towards a more natural approach. It is collected underground and sometimes goes through additional filtration processes.

So you see, bottled drinking water encompasses a wide range of varying parameters. The fact that it isn’t very cheap makes the risk not worth it. I recommend that bottled water should only be used in the case of an emergency. Another solution is Tap Water. It is not hard to turn it into good water for your fish tank. Check link.

Can I Put Seashells In My Fish Tank? 

Adding seashells to your fish tank offers a certain visual appeal. However, it is important to note that seashells cannot just be added indiscriminately to fish tanks. 

Seashells add calcium to the water. This nifty feature is not useful in your freshwater tanks. 

Objects that can cause chemical changes in the water should really be avoided. The changes may be beneficial, but no one wants to risk any harmful effects.

So, except you get a go-ahead from your local fish tank shop, you should not add seashells to your fish tank.

Can I Put Crystals In My Fish Tank? 

Considering the visual appeal, it seems like a good idea to put crystals in your fish tank. However, all crystals are not the same. 

Different crystals have different chemical compositions and definitely act differently when left in water for a long time. 

A general rule of thumb, just as with seashells above is to avoid any object(s) that may set off a chemical change in the water.

Before putting any crystal in your fish tank, I would recommend you find out the chemical composition of such crystals just to be sure it doesn’t contain any dangerous metals. 

Generally, crystals that contain zinc, copper, or aluminum, or crystals that are water-soluble should be avoided as they could harm your fish. 

Also, look out for crystals that have a fibrous consistency. They tend to become soluble over time. Oxidized crystals should also be avoided. 

If after your research, you find out the crystal you’re interested in poses no threat to your fish or even has a beneficial role to play in the chemical composition of your water, then you can go ahead and put them in your fish tank.

Can I Put Bamboo Wood In My Fish Tank? 

Bamboo wood would give a more natural look to your fish tank.

However, you should note that wood will generally decompose after a while and this is not something you want happening inside your fish tank. 

If you want to put bamboo wood in your fish tank, ensure that the wood has been treated and is harmless to your fish. Ask your local pet shop for treated bamboo wood.

An alternative to this is to put a live plant. I found that Dracaena Sanderiana, commonly known as lucky bamboo is a perfect fit for this purpose. 

Lucky bamboo looks like bamboo, but it is more adapted to aquatic habitats. As a matter of fact, putting lucky bamboo in your fish tank will change the ecosystem inside your tank.

You can simply purchase lucky bamboo at your local pet shop or just order it on Link to Amazon.

Can I Put Rocks From Outside In My Fish Tank?

Picking rocks from your surroundings seems like a great way to save money while adding to the beauty of your fish tank. Especially if you found a really unique looking rock and you think it would look great in your fish tank.

There are so many types of rocks all around us and they all have different chemical compositions. So we cannot assume that because a certain rock is safe to add to your fish tank, another one that looks like it would also be safe for your fish tank.

Before dropping that rock into your fish tank, you need to ensure that rock is clean and it does not pose a threat to your fish.

A simple way to do this is to wash the rock to remove any contaminants and dirt, and then place them in a bucket of the same water you use in your fish tank. 

Test the usual chemical parameters of the water immediately after putting the rocks in, and then test them again after the rocks sat in the water for about a week.

If you notice any significant changes in the chemical parameters of the water, this is a clear indication that the rocks should not be used. 

I personally prefer this method to use vinegar. Vinegar only tests for the presence of calcium, but there several other parameters that we must consider. Hence the one-week wait is totally worth it in my opinion. 

Can I Put Table Salt In My Fish Tank? 

Table salt usually contains iodine potassium. Remember, table salt was made for human consumption. Table salt is mostly sodium chloride that contains iodine and potassium.

Sodium chloride in its pure form can be put in your fish tank for a number of reasons including preventing infection. However, table salt, because of the additives it contains should not be used in your fish tank.

Fish generally need iodine, but it is already contained in their food. Too much of iodine could prove harmful to your fish. The caking agent, on the other hand, is downright dangerous to your fish. 

If you must put salt in your fish tank, ensure that it is aquarium salt which is pure sodium chloride. It inhibits the growth of algae and also keeps many pathogens and fungi away from your fish.

It is also worth mentioning that some fish are very sensitive to salt and even a little quantity in the water will adversely affect them. Hence, it is advisable to find out how your fish react to salt first before putting salt in your fish tank. 

Can I Put Coins In A Fish Tank?

Coins are typically made of metal. Metals, when left in water for a prolonged period of time, tend to leech into the water. 

Since different countries have different coins and these coins tend to contain different types of metals, it is generally safer to decorate the outside of your fish tank with coins. That way, there is no possibility of metals leaching into your water. 

Another hack I saw is to seal the coin in plastic before putting it in your fish tank.

In conclusion, I would not recommend putting a coin in your fish tank at all. There are other more appealing and beneficial objects that are much safer to put into your fish tank.

How To Make Sure That Fish Tank Decorations Are Safe?

If you are concerned about the effect(s) your decorations will have on your fish, it is usually safer to buy your decorations from your local pet shop.

The decorations get from pet shops are usually graded to ensure that they are safe for your fish. However, if like me, you also had a few objects you wanted to add to give your fish tank a certain personality, you need to consider the following questions:

  1. Is it going to change the chemical parameters of the water?
  2. Is it sharp enough to injure my fish?
  3. Is it shaped in a way that can trap my fish?
  4. Is it consumable?
  5. Is it degradable?
  6. Is it painted?

If any of your decorations answered yes to any of these questions, the best course of action is to exclude it. As the old saying goes “it is better to be safe than sorry”.

Good knowledge of the composition of the objects you want to put into your fish tank as well as the impact they will have on the water and your fish is the best bet when you want to put anything into your fish tank. 

When you know exactly what you are putting into your fish tank, you can easily steer clear of harmful objects and only put safe objects into your fish tank. Always remember: when in doubt, do not put it in until you know for sure. 

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