Eight things to avoid putting in the fish tank

We add different accessories to improve the aesthetic of the tank. There are plenty of decorative items like colorful pebbles, rocks, crystals, coconut shells, and much more that you may choose from the fish store. However, sometimes one wrong choice may cost you your adorable fish. Sometimes adding a few foreign items could pose a real threat to the well-being of your fish and tank.

Therefore, today, we are with a list of some of the items that you should completely avoid putting in your fish tank. So check it out, make better decisions, and safeguard your fish.

Objects with sharp ends

Just like we avoid coming in contact with sharp objects, our fish too need protection from them. Many times some decorative items like rocks have sharp points that can harm fish. Therefore, whenever you buy any stone, pebble or crystal check it thoroughly by putting it in your hand for any sharpness. Make sure it doesn’t have any pointed ends and is smooth. While playing fish may get hurt with such objects, get bruises, and harm them.

Eatables other than fish food

Fish generally munch upon everything that you will put in your tank. Apart from feeding them fish food, giving some of the fruits and vegetables is also fine. However, sometimes people put fried food, chips, bread, and related food which is a strict NO. Although fish will consume them, they will cause more harm than good. You should never put any random food to the tank until you know whether it is safe for the fish consumption or not.

Other than being harmful to the fish, such food also deteriorates the quality of water in the tank. For instance, chips contain salt and oil that mix with water and drop off its quality. It will change the water parameters entirely. Therefore, stick to regular fish food and do not feed everything that your other pet could eat.


Chemicals not only change the water parameters, but they can significantly affect aquatic life. People tend to think that the way chlorine used to clean the pool water; it will work likewise in the tank as well. Chemicals should be avoided as far as they are explicitly meant for the tank. When there are living creatures in the aquarium, any chemical could pose a danger to their life. Even a small amount can do significant damage.

Roadside Rocks

Decorating the tank using rocks is not new. You can find plenty of colorful and beautiful rocks at fish stores. They are treated and are safe for the aquarium. On the other hand, the rocks from outside are dirty and have plenty of harmful microorganisms. No matter how properly you wash the rocks until they are not treated, they are not safe to add to the tank. Roadside rocks can alter water chemistry and even change the color of the water. They are not safe for the fish as well. So, always go for store rocks rather than any random rock collected from outside.


Wood certainly is one of the best decorative items for tanks but putting any wood is not a good idea. Woods need to be treated before introducing them to the tank. Tannin, one of the chemicals present in the wood could pose serious harm to the fish. Therefore, always go for the woods that are sold in the fish store. They are well-treated. If you find a nice wooden decorative item outside, wash and boil it properly to remove the impurities. However, this is not the best way to make it aquarium-ready. Once you add wood, change the water regularly as it may alter the color and chemistry of water.

Fish from river or ponds

You might catch a beautiful fish in the river or pond and want to add it to your tank. Beware; it’s a terrible idea. There are two good reasons to avoid adding fish to the tank. First of all, they might carry diseases from their wild homes to your tank and infect your fish as well. Secondly, this practice is not safe for them, as well. Fish need time to acclimatize to the new environment. Adding directly from the wild environment to the new one puts them to stress that may eventually lead to their death.

Snails or worms from outside

Just like fish, you should also avoid adding any wild snail or worm from outside. Easy to find anywhere, the temptation to add them directly to the tank rises. Such snails and worms might be the carrier of some harmful microorganisms that can pose a threat to the fish. Instead, go for the bloodworms and snails that are found in the fish store. They are safe for the fish and can mingle with them easily.

Metallic objects

Some metals release toxins to the environment. Some might rust when coming in contact with water. Both toxins and rust are harmful to the aquarium. Therefore, try avoiding metals in the aquarium unless they are specially made for the tanks and are aquarium safe. Likewise, do not add coins to the water. Coins corrode and release harmful toxins to the water, changing its chemistry altogether.

How to know what is safe for the tank

The above list has some of the most common things people put in their tank, sans knowing their harmful effects. There could be a lot more things which one way or the other are not apt for the aquariums. So, what next you can do is gather more information about them. The three major things that you need to ponder include-

Ask someone from the pet store– People working at pet stores have a good knowledge about the things that are safe for the tanks. Call the pet store from where you bring your tank and fish. They can provide you good information. Do not hesitate in asking as it might cost you your precious water creatures.

  1. Search online– Internet is one of the best sources to gain knowledge on different things. You may research on aquarium-safe decorative items and do likewise. There are multiple forums and websites that deal with fish and aquarium where you can probably get the answer. Similarly, YouTube is also a good source.
  2. Use your own knowledge and common sense– If you are unsure of any particular product be double and triple sure about it before introducing. Gather knowledge from all the sources you can and imply it accordingly. Use your commonsense. Know the composition of the product and find out how it will react with water.
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4 thoughts on “Eight things to avoid putting in the fish tank

  1. Tarun says:

    Very helpful information. I am new to managing aquarium at my home so thie information helped me to understand more. I would look for more information about fish matching,(what type of fish can go with other in a aquarium)

    • Wiquar ahmed says:

      Mango platt Red swordtail. Red mosaic mixed guppy and malepartly and guppy red. can we keep all this fish in one tank with out loosing them

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