Aquarium Rock: Guide to Types of Aquarium Rocks & More

What is the Best Rock for Aquariums?

There are many different types of aquarium rocks to choose from, and they are all beneficial in their own ways. It is largely dependent on the species of fish and plants that you are housing in your aquarium which type of aquarium rock will do best. This guide will help you decide which aquarium rock is best for your needs.

Table of Contents

Aquarium Rock Types

Seiryu Stone

Seiryu Stone is a beautiful Japanese stone that is a dark gray coloration with a bluish hue and white vein-like markings that run through it. It is a popular choice for aquarium aquascaping as it provides a stunning natural look. Named for the Azure Dragon, a mythical constellation of a dragon with vibrant blue scales.

Seiryu Stones have become very popular in the aquascaping hobby, and they are now available for purchase outside of Japan, but you have to be careful when purchasing as there are a lot of stones out there that are mislabelled as Seiryu Stone. So much Seiryu Stone was being sold that there are now regulations on how it is sold.

With regulations on Seiryu Stones, and it being more difficult to get, you have to make sure before you purchase that you are in fact getting the correct stone for your aquarium. True Seiryu Stones are dense because they are made up of limestone. The limestone in the Seiryu Stone is an example of an active stone, this means that it helps the water by raising the pH and helping it maintain at a higher level.

Pros of using Seiryu Stone

Seiryu Stone is beautiful and provides your aquarium with a natural look.
Composed of limestone, Seiryu Stone helps raise the pH of your water, and keep it at a consistent level.
Seiryu Stone is very dense, and for this reason it is often used to create natural looking caves and hiding places for your fish to explore and hide.
Seiryu Stone is naturally porous allowing for the growth of beneficial microorganisms.

Cons of Using Seiryu Stone

Due to this stone being very dense, you will want to make doubly sure that it is secured so that it does not shift when in the aquarium. Heavier stones can be harmful to fish if they fall on them or get trapped under them.
Seiryu Stone is hard to get ahold of, and if you can find Seiryu Stone for sale, it is very pricey.
There are many look-alikes out there that are misrepresented as Seiryu Stone, so if you are wanting to purchase some for your home aquarium, you will want to make sure that you know how to identify it. True Seiryu Stone has a bluish hue to the main dark gray coloration, as well as fine white lines that run through the stone like veins.

Dragon Stone (Ohko Stone)

Dragon Stone is a sedimentary rock. This means that Dragon Stone is formed from deposits on the Earth’s surface. They are formed from rocks that were already there, or from once living organisms. Dragon Stone is a popular choice for aquascaping due to its natural look, and scaly texture. It also resembles petrified wood in its appearance. Dragon Stone is sometimes mistaken for an artificial stone due to its looks.

Dragon Stone contains clay, minerals, silt, and organic matter that was all pushed together with high pressure water waves during its forming process. It is more lightweight, and versatile than other types of aquarium rock.

Due to the popularity of Dragon Stone for home aquariums and how long it takes Dragon Stone to become mature enough, true Dragon Stone from Japan can be difficult to get your hands on. Luckily, there are other places you can purchase Dragon Stone. Dragon Stone does not affect the pH of the water.

Pros of Using Dragon Stone

Dragon Stone is made up of clay, minerals, silt, and other organic matter that can be beneficial to your aquarium
Since it is made up of mostly clay, Dragon Stone is a lot more lightweight than you might expect from looking at it. This makes it less dangerous to your fish if it happens to fall down.
Dragon Stone is easily recognised, but the look of it can vary depending on where it is purchased.
Dragon Stone does not affect the pH of your water.

Cons of Using Dragon Stone

Dragon Stone is very fragile. Its largely pitted, porous surface makes it easy to break. Even cleaning can cause chipping of your Dragon Stone if you are not careful. Dropping it could cause large pieces to shatter.
Dragon Stone accumulates waste and debris requiring cleaning more often, which can cause damage to the stone, or cause problems with your water parameters.

Lava Rock

Lava Rock is exactly what it sounds like, rocks that have been created by geothermal conditions. After a volcanic eruption, the molten rock cools and forms into the commonly found porous rocks that can be used in aquascaping. Due to how the Earth forms its crust, Lava Rock is plentiful on our planet.

Pros of Using Lava Rock

Lava Rock is a plentiful resource on our planet and it is not only eco friendly, it is biodegradable, and not as expensive as other aquascaping stones.
Lava Rock is used in aquascaping to help break up the lines of sight for fish. This is especially helpful when housing more aggressive or territorial fish.
Lava Rocks do not affect the pH of the water like other rock type hardscaping material so you can use as much as you want without worry.
Lava Rock is porous and it allows for the growth of beneficial bacteria.

Cons of Using Lava Rock

Due to the way Lava Rock is formed, it has sharp and rough sides. This could be dangerous for particularly active fish if they run into or bump the Lava Rock.
Lava Rock is less dense, so it will need to be securely placed into your aquarium so that it does not get disturbed and fall on your fish causing injury.
Lava Rocks have to be monitored and cleaned more often due to their porous surface it is much easier for fish waste and leftover food debris to become trapped on the surface of the rock.
If bumped or scraped onto the sides of the tank it could potentially scratch the glass of your tank if you are not careful when placing it.

River Rock

River Rocks are often used in aquariums for aquascaping for their natural look. River Rocks come in many shapes, sizes, and colorations which makes it easy to achieve the look you are going for. As River Rocks have a naturally smoothed surface, they don’t run much of a risk of harming your more active fish that may run into them. However, they could potentially harm your fish if they are not secured into place and they fall.

River Rocks can affect the pH of your water depending on the River Rock itself. Some River Rocks are made of limestone and as it naturally deteriorates it can raise the pH of your water and help maintain it at a higher level. River Rock is possibly one of the most cost effective materials to use in aquascaping as they can be found outside. It is important to know which type of rock that you are collecting, and how to prepare it properly for your aquarium.

Pros of Using River Rocks

River Rocks can be found outdoors quite easily, and they come in a wide variety of shapes, sizes, and colorations.
Some River Rocks can alter the water parameters and naturally raise the pH level of your water which can be very beneficial for some aquariums.
River Rocks provide a more natural look to your aquarium, and can be used as barriers that break up the line of sight for your fish. This is especially helpful for fish that are territorial or aggressive.

Cons of Using River Rocks

River Rocks gathered from outside need to be checked and prepared before they can be added to your aquarium as they could potentially introduce harmful contaminants into your aquarium.
River Rocks are heavy, so you will want to choose how many you place in your aquarium with care as well as make sure that they are secure so they don’t fall and injure your fish.

Petrified Wood

Petrified Wood is a type of rock that was once wood. It is just the fossilized remains of a tree. Petrified Wood is a popular aquascaping material that is popular for its interesting look. It resembles Dragon Stone, Lava Rock, or even tree wood. It is important to know that even though it resembles a living tree, it is not. It once was a living tree, but over time all the parts that were living were replaced with sediments of compressed sand. It is a type of inert stone. This means that it will not affect the pH of your water at all. However, Petrified Wood can have different color variations. These colors are actually minerals that can break down over time and affect the pH of your water. It is important to make sure that you choose your Petrified Wood for your aquarium with care, and not only clean it thoroughly, but also monitor your water parameters regularly.

Pros of Using Petrified Wood

Petrified Wood provides a more natural look to your aquarium without causing the pH to change.
Petrified Wood can come in many different shapes, sizes, and even colors. It offers a barrier for fish that are territorial or otherwise aggressive.

Cons of Using Petrified Wood

Even though Petrified Wood comes in a variety of colors, you should take note that sometimes the colors that make up Petrified Wood can be harmful to your aquarium. The colors are mineral deposits that can break down and change the pH of your water.
Petrified Wood has a pitted surface that will need to be monitored and cleaned regularly.
Petrified Wood can take a long time to get aquarium ready, sometimes needing to be soaked for weeks at a time to make sure that it is clear of contaminants that will not affect your water, fish, or plants.

Hakkai Stone

Hakkai Stone has become a popular choice for aquariums, and is often used in aquascaping. It first gained popularity in Japan, and has only increased in popularity over time. Hakkai Stone has texture to it that gives it more character than smooth River Rocks, but less texture than Petrified Wood. Hakkai Stone is a darker colored stone that has some whitish or brownish colorations to it. Hakkai Stone comes in many shapes and sizes so finding the right Hakkai Stones to fit your aquarium won’t be difficult. Hakkai Stone is a type of inert stone which means that it will not change the pH of your water.

Pros of Using Hakkai Stone

Hakkai Stone is a great stone for aquascaping as it is not particularly rough enough to cause injury to overactive fish if they happen to run into it.
Hakkai Stone is a type of inert stone. This means that it will not cause the pH of the water to change over time.
Hakkai Stone is available in many different sizes and can be colored differently too. This makes finding the correct Hakkai Stone for your aquarium fairly easy.

Cons of Using Hakkai Stone

Hakkai Stone can be quite pricey. You can expect to pay around $60 for a 5 pound rock.
Hakkai Stone is quite heavy and will need to be placed securely in your aquarium so that it does not fall and injure your fish or plants.
It is important to clean your Hakkai Stone regularly as the pits on the surface can accumulate fish waste and leftover food debris. If you let it build up too much, it can negatively affect your water parameters.

Elephant Stone

Elephant Stone is sometimes referred to as Elephant Skin Stone due to how closely it resembles the skin of an elephant. It is also sometimes just referred to as Gray Stone. Like other stones, Elephant Stone provides your tank with a more natural look as well as gives your fish places to explore and hide. You can also use Elephant Stone strategically to break up the line of sight for your fish that are territorial or aggressive.

Elephant Stone is formed naturally. It is composed of limestone. It is an example of an active rock as it will work to raise the pH of the water and help maintain it at this higher level.

Pros of Using Elephant Stone

It can provide your aquarium with a more natural look with many shapes and sizes available.
Elephant stone is a type of active stone that will help you maintain a higher pH in your aquarium.
Elephant Stone can help break up your aquarium to allow for your more territorial fish to have their own space as well as allowing your other fish places to explore and hide.

Cons of Using Elephant Stone

Elephant Stone does not do well in freshwater, and if left unchecked it can drastically alter your water parameters. It is always best when using this stone to perform routine water checks so that you can quickly correct any problems as they arise.
Elephant Stone is heavy, and it will need to be properly secured in your aquarium so that it can not fall down and cause injury to your fish or plants.
Elephant Stone can scratch your aquarium glass if you are not careful when you place it, or during cleaning.

Black Rock

Black Rock is a type of hewn stone. This means that it is cut from a much larger stone into shape. Black Rock is great for aquascaping as its dark coloration creates a stunning contrast with your fish and plants. These stones are angular and uniquely shaped. They also come in many different sizes. Black Rocks are a type of active aquarium stone that will change the pH of the water over time and raise it. It is important to monitor your aquarium when you use Black Stone.

Pros of Using Black Stone

Black stone creates a beautiful contrast for your fish and plants in your aquarium and helps them stand out.
Black Stone comes in many shapes and sizes

Cons of Using Black Stone

Black Stone is dense, which means that it will need to be properly secured in your tank so that it does not fall and injure fish or plants
Black Stone can alter the pH of the water, so you will need to frequently monitor it for changes.

Slate Rock

Slate Rock is a type of rock that is typically flat, gray stones that are used commonly in aquascaping to create barriers and caves for your fish to explore. Slate Rock is a type of active stone that will raise the pH of your aquarium. The more Slate Rock you put in your aquarium, the more it will raise the pH.

Pros of Using Slate Rock

Slate Rock is a flat rock which makes it easier to create caves and barriers for your fish. This is particularly helpful if you have fish that are protective of their territory.
Slate Rock is a common rock that is fairly inexpensive to purchase

Cons of Using Slate Rock

Slate Rock needs to be secured in the aquarium to prevent it from falling onto your fish or plants
Slate Rock will raise the pH of the water so you will need to monitor your water parameters regularly.

Texas Holey Rock

Texas Holey Rock is often called Honeycomb Limestone. It is a type of limestone that comes from Texas and like the name suggests, it is filled with large holes. It is an example of a type of active stone that will change the pH of your water.

Pros of Using Texas Holey Rock

Texas Holey Rock looks amazing in the home aquarium, and provides your fish with many places to explore and hide.
This type of aquarium rock works great for Cichlid tanks.
It is very cost effective at around $2 to $4 per pound.

Cons of Using Texas Holey Rock

Texas Holey Rock will affect the pH of the water as it is made up of limestone. It will raise the pH of your water, and should be monitored regularly.
Texas Holey Rock needs to be cleaned regularly so that it doesn’t collect debris or waste.

Reef Rock

Reef Rock is a type of live rock that is often used in saltwater tanks for aquascaping as there are many species of fish that rely on coral reefs for their food and shelter. Living Reef Rocks are quite interesting to watch as they grow. Reef Rocks are an example of an active aquarium rock as they will raise the pH of the water.

Pros of Using Reef Rock

Reef Rock helps with the biofiltration of the water, and will ultimately help you keep your tank more clean.
Reef Rock is vital for some types of fish for not only food but shelter as well
Reef Rock is stunning to look at.

Cons of Using Reef Rock

Reef Rock increases the pH of the water and is not suitable for freshwater aquariums for this reason

Can Any Rocks Be Used in an Aquarium?

It is possible to use many types of rocks in your aquarium, but you will need to make sure that your rocks are clean before you introduce them, and that they are not a type of active stone that can affect your pH. Unclean rocks can introduce harmful bacteria into your tank that will harm your fish and plants. Some rocks need to be cleaned and soaked for weeks to make sure they are aquarium ready.

What Rocks are Not Safe for Aquariums?

You will want to be mindful of the types of rocks that you are placing in your tank. Some rocks can help you maintain the correct pH of the water, and some do not affect it at all. When choosing a rock that affects the pH of the water, you will want to make sure that it is not too highly concentrated as it could do damage to your tank’s inhabitants.

You will also want to avoid rocks that have sharp, jagged edges as they could cause injury to fish that run into them. Smooth stones are a much better choice for aquariums with active fish.

How to Aquascape with Rocks

Aquascaping with rocks is fairly straightforward. You just need to be aware of the type of rock that you are using as some can change your aquarium water parameters. Aquarium rocks also need to be monitored and cleaned regularly so that harmful waste and debris do not build up in the crevices or pits of the rocks. The most important thing when using rocks in your aquarium is making sure that they are secure. Rocks that are not secure could fall down and injure your plants or fish.