Can You Use Rocks From Outside for an Aquarium?

Aquariums are a beautiful way to keep fish, but they can’t do it alone. The substrate, lighting, and decorations all play an essential role in the health and happiness of your fish, and one of the crucial substrates is rocks.

If you don’t have access to expensive rocks in the market, you can use stones from outside to supplement an aquarium. Rocks provide a good base for the aquarium and help to keep the water clean. They also add interest to the tank and can be used to create areas for fish to live or hide.

How Do You Tell if a Rock Is Safe for an Aquarium?

You can use rocks for aquariums, but it is vital to ensure that they are safe for the fish. There are a few things that you can do to check if a rock is safe for an aquarium:

  1. Look at the size of the stone. Big rocks will be harder to move and may cause more harm to the aquarium than small rocks.
  2. Look at the shape of the rock. Rocks that are round or squarish are usually safer than jagged ones or have sharp edges.
  3. Look at the surface of the rock.

It is smooth and has no cracks or bumps; it is probably safe for an aquarium.

How to Test Rocks for an Aquarium?

Testing rocks for aquarium use is simple. All you need are some wet stones or a small container of water. If the rock is clean and free of any toxic or poisonous material, you can use it in an aquarium.

Many types of safe rocks can be used in an aquarium. Some of the most common safe rock types include gravel, crushed coral, and decorative rocks. Gravel is the most affordable and can be found at most pet stores. It is easy to clean and provides a suitable substrate for plants and fish. Crushed coral is a more expensive option, but it gives a natural look to your aquarium and has been proven to help with bacterial growth. Decorative rocks can add personality to your tank and come in various shapes and colors. Be sure to choose safe rocks for fish as some types can release toxins if ingested.

Safe Rock Types for Aquariums

Many types of rocks can be used safely in an aquarium, but you should not use some because they can be dangerous to fish. The most important thing to remember when choosing rocks for an aquarium is to select safe ones for the fish. Some of the safest types of rocks for aquariums include:

Slate and Shale

There are a few safe rock types for aquariums, including slate and shale. Both of these rocks are composed of several small, rounded pieces of rock that have been glued together. Because these rocks are made up of smaller pieces, they won’t create as much noise when moved around or touched, making them a good choice for quieter tanks. Both slate and shale can be used in saltwater tanks as they won’t rust.

Lava Rock

There are many safe rock types for aquariums, but lava rocks are a perfect choice because they come from the earth’s mantle and have high heat and mineral content. This makes them an excellent substrate for fish and other aquatic organisms that need plenty of minerals to thrive.


Quartzite is a safe rock type to use for aquariums. It is a type of sandstone and is very durable. It will not break easily, making it a good choice for tanks that have heavier items on top or bottom.

Glass Rocks

Glass rocks are safe for aquariums; they are one of the most famous rocks used in tanks. They come in a variety of colors and styles, so you can find one that works with the décor of your tank. Some people choose to use natural stones outside their homes, but be sure to clean them first. Safe rock types for aquariums include granite, basalt, and marble.

Rainbow Rocks

Rainbow rocks are a type of rock that you can find outside. These rocks are safe to use in an aquarium, but you should not use some kinds of rainbow rocks because they can cause sediment to build up in the tank. Other types of safe rock can be used in an aquarium, so choosing the right style for the tank is crucial.

Plastic Rocks

You can use rocks from outside for an aquarium, but they must be safe when selecting rocks. Some types of rocks can create hazards for the fish and are not safe to use in an aquarium. Plastic rocks are a good option because they are safe and do not create any risks.

Texas Holey Rocks

Many people think that you can use only rocks from inside a lake or cave in an aquarium. However, many safe and fun rock types can be used for any aquarium. Texas holey rocks are one example of rock perfect for use in an aquarium. These rocks have been worn down by water and wind, making them extra safe for fish and other aquatic creatures.

Where to Find Rocks for the Aquarium?

You can find rocks all around us. Some are easy to find, and some have to look a little more complicated. For example, rocks for an aquarium can come from outside or on the ground. If you are looking for rocks that are easy to find, you can go to the park or a nearby river and look for rocks that people have thrown away. If you want to see more hard rocks to get your hands on, you can go out digging in your yard or looking in caves.

How to Pick Rocks for an Aquarium?

When choosing rocks for an aquarium, consider a few things. First is the size of the rock. The second is the type of rock. The third is the shape of the rock. Fourth is the color of the rock. Fifth, whether or not the rock is porous. Sixth, how many stones are needed. Seventh and finally, where to buy rocks for an aquarium. The size of a rock can be important when choosing them for an aquarium because some rocks are more significant than others and will need to be placed in a specific location to look good in your tank. Some rocks can also create obstacles for fish if placed in an inappropriate area and may need to be avoided if you want your fish to feel comfortable swimming around their tank. 

How to Clean River Rock for an Aquarium?

Cleaning river rock for an aquarium can be a bit of a challenge. Many of the chemicals used to clean other surfaces may damage the rocks. Some people use a mixture of water and vinegar to clean the rocks, but this approach is not always successful. Using a method that does not require any chemicals is essential, as this could damage the rock over time.


Rocks can be used as substrate in an aquarium but must be scrubbed clean with a brush. The rocks should be rinsed and dried before being added to the tank.


Rocks from outside can be used as substrate in an aquarium, but it is essential to soak them in pure water before adding them to the tank. This will remove any harmful chemicals that may be on the rocks.


Before using rocks from outside the home for an aquarium, consider a few things. First and foremost, make sure that the rocks have been thoroughly washed with boiling water. This will remove any contaminants that may be present. Next, it’s essential to decide where to place the rocks in the aquarium. Some aquarists prefer to put them at the bottom of the tank, while others place them near the top. Ultimately, it’s up to you how you want to arrange them.