Best Rocks for Freshwater Aquarium in 2021

Whoever heard of buying rocks for freshwater aquariums? Many people live near a river or a lake, so why not just head on down and pick up a few to bring home and make a family day out of it? There are actually many factors that make this a terrible idea. As many seasoned aquarists will know, getting the water conditions just right for your fish tank is a science. Adding random rocks from nature will alter all your hard work and change the acidity and other chemical reactions in the water.

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We understand that purchasing rocks, something found in the outdoors may sound a little counter-intuitive, but trust us, it’s necessary. Aside from all the aquarium rocks for purchase are already treated to be safe for your fish tank, a lot of them are also carefully selected to create the perfect aquascape to match your fish’s natural environment. Of course, they have more functions than just “looking pretty”, and that’s what we will get into today with the best rocks for a freshwater aquarium.

1. Best Value: Royal Imports 5lb Large Decorative Polished Gravel River Pebbles Rocks

Royal Imports Polished Gravel River Pebbles Rocks

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For budding aquarists or those who don’t want to take up too much space, these polished gravel river pebble rocks pave the bottom of your fish tank and make great substrate. You can pick from different colors and sizes to fit your needs. What’s important to know about these pebbles is the fact that they are natural. Natural rocks are non-toxic and eco-friendly.

Also, because they are from nature, they also last longer than their artificial counterparts. If you have small tanks and a lot of these rocks left over, you can think about using the excess river rocks as home decor. These polished gravel river rocks from Royal Imports can pave your walkway, decorate your flower beds or just sit in the fish tank and preserve your nitrate levels.

Related: Types of Fish Tank Rocks

Pros:

Why We Like It

We like these rocks because they come in a variety of colors and sizes. Not only that, these rocks will protect the water chemistry of your tanks and are great additions to your freshwater aquarium.

2. Best Budget: SACKORANGE 2 LB Aquarium Gravel River Rock

SACKORANGE Aquarium Gravel River Rock

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SACKORANGE is your affordable freshwater aquarium rocks that are completely natural and smooth due to some minimal polishing. Each 2-pound pack has rocks that come in a variety of colors that will brighten up your freshwater aquarium. The stones have gone under treatment to be long-lasting for your tank and other home decor needs. Each piece measures approximately 1-inch in size, which makes them safe for fish species that tend to dig and eat smaller pieces of gravel.

The polished surface also makes the rocks safe and easy for you to handle. We know a fair share of people who have unnecessary scrapes and cuts from jagged rocks but these rocks for freshwater aquariums won’t pose that risk.

Pros:

Why We Like It

Although these rocks come in smaller packages, you may still end up with a few extra pounds, and they make great additions to your outside walkway, inside flower vases and more.

 

3. Penn-Plax Reptology Shale Step Ledge for Aquariums

Penn-Plax Reptology Shale Step Ledge for Aquariums

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For those who are looking for more than aquarium liner stones, the Penn-Plax Reptology Shale Step Ledge is a great addition to your tanks as they are more of an aquascaping rock. A rock as versatile and high quality as this one, it can be used for reptiles, fish and other aquatic pets. If used for turtles, the Penn-Plax step ledge rock can also double as a basking platform.

When the shale step ledge rock is used in an aquarium, it will be a cave ornament and used for freshwater fish to hide in. The step ledge is beautifully painted to mirror a live rock and is made from 100% safe and non-toxic materials.

Pros:

Why We Like It

We like the Penn-Plax step ledge rock because it adds a special touch to your tank where other items don’t. Placing this rock into your aquarium won’t alter the pH balance or water chemistry.

4. CURRENT USA Seiryu Stone Collection

CURRENT USA Seiryu Stone Collection

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This next freshwater rock for your aquarium is an even better stone for aquascapers. The menacing look can create quite the environment for your fish. The Seiryu stone is a popular choice for many fish owners due to its appearance. Each stone was selected by hand and sculpted in such a way to feature sharp edges, crevices and cuts. The unique shapes will allow you to plan an amazing blueprint for your freshwater aquarium.

Related: Seiryu Stone – A popular aquarium stone decor

Sure, it looks great, but is it safe? These stones are 100% safe for all creatures that may inhabit your tank. It will make changes to the aquarium water when used and they come ready to place in the box. All the stones are prewashed and come with a 30-day guarantee.

Pros:

Why We Like It

No treatment needs to be done on your end for these rocks. They come ready to use and if you find a defect in the product or are unsatisfied, Current USA offers a 100% return.

5. Lifegard Aquatics Dragon Rock Kit

Lifegard Aquatics Dragon Rock Kit

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Just the name alone suggests these metamorphic rocks will look great in your fish tanks. They look like dragon scales and are 100% natural. Unfortunately, these beautiful rocks are not suited for saltwater tanks. Even for your freshwater aquarium, we would recommend washing each piece thoroughly before adding them to your tank to preserve the pH and hardness of the water.

These rocks also come in different shades and come in different sizes to help add dimension to your aquarium. Each pack is ready for a 25 gallon tank, but there are also 10 gallon packs available. You may need to purchase more than one pack if you have larger freshwater aquariums.

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Pros:

Why We Like It

Lifegard Aquatics dragon stone features a very unique look that resembles a dragon’s scales. When in the water, they will add a very specific feel to the tank and are great for cichlid tanks.

6. Pisces 17lb Seiryu Rock for Aquascaping

Pisces 17lb Seiryu Rock for Aquascaping

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Pisces is our second Seiryu aquascaping rock option on our list. This option is just as high quality and comes in a lighter color for your tanks. They are suited to fish of all life stages and freshwater species. Seiryu rocks are a type of dragone stone. In Japanese, Seiryu means azure dragon. In Asian culture, dragons are mystical protectors that are positive omens.

Adding this Seiryu rock into your freshwater tank will not only elevate the appearance but add meaning as well. Aside from being a great match for freshwater tanks, these stones are also a good fit for terrariums and vivariums on a dry landscape.

Related: Funky Freshwater Fish

Pros:

Why We Like It

A Seiryu rock is safe for your aquariums and also adds a touch of luxury to the appearance. The white color makes them that much more special than regular dark dragon stones.

7. Midwest Hearth 100% Natural Lava Stones

Midwest Hearth 100% Natural Lava Stones

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Back to paving the tank, Midwest Hearth offers 100% natural lava stones that are not artificially treated in any way. As lava stones, they are very resistant to heat, which makes them extremely durable rocks that require little to no maintenance. Naturally formed, these lava rocks will not break or fade. The only treatment they have gone under is tumbling, which is conducted to make sure each piece comes out smooth and round, eliminating sharp edges.

In each pack from Midwest Hearth, you will get 1o pounds of lava stones that are suitable for your tank, outdoor walkway paving, flowerbed or vase decoration, and aggregated landscapes. You can also think about using these rocks in your fireplace or fire pit thanks to their heat resistance.

Pros:

Why We Like It

Anything that will keep well and requires zero maintenance is a plus in our books. Lava rock is one of the best rocks for your freshwater aquarium due to its durability.

8. Capcouriers Small Slate Stones

Capcouriers Small Slate Stones

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Capcouriers is a new type of rock on our list, a slate stone looks exactly like the name suggests – little slates. These high quality and luxurious-looking stones are small, about 2-4 inches in length. They are meant to be piled on top of each other to create little mounds or they can be used to line the aquarium bottom. Not only do the sizes vary, but the shapes and colors do as well.

One thing to keep in mind with freshwater aquarium rocks is that they need to be rinsed before they can be placed in your tank. You may notice your slate stone is a very light pearly grey before rinsing, but it will end up being a dark grey after a thorough wash.

Pros:

Why We Like It

It may be a personal preference, but we think these rocks are very beautiful. Placing a slate stone combo in your freshwater tank along with other types of rocks can really enhance the look.

9. Lifegard Aquatics 25G-Smoky Mountain Stone

Lifegard Aquatics 25G-Smoky Mountain Stone

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These Lifegard Aquatics smokey mountains stones are the same as Seiryu stones or dragon stones. You can choose from different packaging options that include 1-4 packs. We do realize the price of these rocks for aquarium decoration is quite steep, but the high quality of these natural stones and their ability to maintain the pH balance of your freshwater tanks are worth the price.

They look like real rock formations and will improve your overall tank setup. Your fish will love to explore these rocks for freshwater aquarium tanks, which come from a trusted brand that specializes in aquatic decorations.

Pros:

Why We Like It

You can never go wrong with Seiryu dragon stone whether you want it as a cave ornament or just to place around your tank. They offer a type of versatility not often found in other rocks.

10. CJGQ 20 lb Black Pebbles for Fish Tanks

CJGQ 20 lb Black Pebbles for Fish Tanks

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Sometimes aquarists want to be as simple as possible and not draw attention away from their beautifully-colored fish. If this is the case, a freshwater aquarium lined with black river rocks is a great choice. The ones from CJGQ are natural, non-toxic and eco-friendly. Not only are they one of the best rocks for freshwater aquarium setups, but they can also be used for multiple other purposes such as paving your walkway, sitting indoors in your flower pots and more.

The surface of these best freshwater aquarium rocks coated in wax to enhance the color and shine. Don’t worry, the pure paraffin wax isn’t harmful to your fish.

Pros:

Why We Like It

The all-black style of these rocks for your freshwater aquarium will preserve the natural look for your tank environment but could have quite a few remaining to decorate other parts of your home.

Best Rocks for Freshwater Aquarium Buyer’s Guide

As we mentioned before, aquarium rocks in your freshwater tank will affect the environment and alter the water chemistry if you don’t purchase suitable ones. In general, natural stones that have minimal treatment are the best. But there has to be more to it than just the appearance, right? What about the composition and type of rock? To help you make the best choice when purchasing rocks for freshwater aquarium setups, our team will break down what to look for.

Type

fish tank rocks

First up is the type of rock you choose. In general, rocks suitable for freshwater aquariums are classified into three main types: Metamorphic rocks, sedimentary rocks, and igneous rocks. In order to choose the right ones, you need to get to know each type a bit better.

Metamorphic rocks

Metamorphic rocks are the most durable of all three types. This is because they have been through the wringer and have been subjected to natural occurrences such as extreme heat or pressure. They are the product of other rock types going through these severe changes. This also means that they are the ones less prone to alterations in your tank and are also low maintenance. Slate rock is a good example of metamorphic rock.

Sedimentary rocks

Sedimentary rocks are formed with sediment. This takes time as layers and layers of small particles are pressed together under pressure to form these rocks. Just like it sounds, sedimentary rocks can be less durable than other types on our list. An example of sedimentary rock is shale.

Igneous rocks

Igneous rocks are beautiful because they possess a glossy sheen and can resemble glass. These are the lava rocks we have on our list that were formed due to the cooling of earth’s natural materials such as lava.

These rocks have very different appearances, so the best way to find one that’s best for you is to determine the type of theme you want to go for and look for the type of rock that corresponds with your needs. Just make sure the one you choose is safe for freshwater aquariums.

The color of these aquarium rocks will also vary depending on the type you choose. If you are going for a certain color scheme, then the type of rock will matter.

Size

Next up is the size. The size of the rock is crucial to the safety of your aquarium inhabitants. Some fish tend to burrow and dig, and others like to eat everything they can fit into their mouths. As you can imagine, ingesting rocks won’t do your aquarium creatures any good. For marine creatures such as these, you would need to purchase larger sizes.

The size also depends on what you are using the freshwater rocks for. If you are using the rocks just for paving purposes on the bottom of the tank, then they will come in sizes ranging from 1-4 inches in length. However, for aquascapers planning to use these fixtures purely for decoration and the entertainment of your fish, then they will come in much bigger sizes.

Aquarium at the CSIRO Discovery Centre
Photo by Carl Davies

Before deciding on how big the freshwater aquarium rocks will be, you need to also take into account the size of your tank. Make sure you don’t overpack it by looking at the labels of the rocks. They will usually come in packs clearly stating how many gallons are included in the package.

Structure and Shape

We then go into the structure of these rocks. River rocks give us less to work with because they come in pebble form. These are the ones that we mentioned that come in 1-4 inches in size are optimal for paving the bottom of your tank. What’s great about these rocks is that any type of tank owner can make do with them. There are plenty of colors to choose from and these types of rocks for freshwater aquarium are purely for decoration.

Related: The Freshwater Aquarium Water Guide

Other than these small round ones, we have the mountain rocks that can come in many shapes and sizes. These are the dragon stones and are also used for decoration. However, they can also be used as separators to allocate territory for certain species of fish or be used to play hide and seek or for exploration.

We also have artificial options, such as the one from Penn Plax that make great caves and hideouts in your aquarium. These aquarium rocks are not natural but are still constructed to be safe for your fish. As an owner, we understand that safety takes precedence but you won’t need to worry about artificial rocks if you purchase them from a reputable brand.

Safety

Speaking of safety for your freshwater aquariums, you want to be sure the ones you choose will not alter the tank water environment. Some fish species are very susceptible to changes in the water and even a 1-2 degree temperature or pH change could be fatal. To make sure you are not endangering your fish, the best rocks for freshwater aquarium will be 100% safe. Just because they are natural doesn’t mean they are safe. They may be more suited to saltwater aquariums rather than freshwater tanks.

You have to be sure the rocks you choose are labeled safe, non-toxic and eco-friendly. The treatment they undergo could involve tumbling and polishing to rid the surfaces of sharp edges. Depending on the type of rock you choose, the sharp edges may be unavoidable. Dragon stone or Seiryu is a good example of stones that have sharpened edges. To administer treatment to these stones would mean losing their unique beauty. If you choose Seiryu, make sure you are careful when handling the stones.

One more thing to be aware of when receiving your stones is that many of them need to be wash thoroughly to make sure there are no surface residues or dust. If you don’t wash them well, they could alter the pH balance and hardness of the water. The best rocks for the freshwater aquarium will always state if they are prewashed.

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Amount

Just how much do you need? If you are thinking about decorative rocks, it’s much easier to grasp how many aquarium rocks you need to meet your requirement. You must leave enough space for your fish to dart in and around the structures without compromising their free space. If you are thinking about gravel or larger pieces of rocks for the bottom of your tank, then there is a lot more to consider.

There are a ton of factors to consider including the type of fish species you have, the shape and size of your tank and the size of the aquarium bed. Aquarium rocks are the best in the sense that they can be used for different things if you end up with extra. Since they come in packs, it’s always advised to purchase more than you need. If at any time you need to replace parts of the gravel or aquarium rocks, you have some excess handy. Otherwise, they are great for landscaping and decorations around your house too.

Each aquarium rock seller will label how many pounds the rocks are or how many gallons they are suited for. In general, the rule is one pound per gallon. This will give you a clearer idea of how much you need if you do the simple math.

Budget

Speaking of how many aquarium rock packages to get, you need to think about your budget. You don’t really have a choice in the matter when it comes to tank size and amount, but the type of rock you choose can vary in price. For example, the small pebble versions are much less costly than dragon, shale or slate stones. The best rocks for freshwater tanks won’t take too much out of your pocket but will look good as well.

Your team advises you not to put appearance before safety. If you go for artificial stones that look gorgeous but have undergone a lot of treatments to look the way they do, you will be compromising your fish.

Maintenance

Aquarium Artis
Photo by Svdmolen

How low maintenance are the rocks? Tank cleaning is one of the worst parts of keeping fish, but it’s a necessary task to keep your fish healthy. A complete overhaul and thorough clean will include removing your fish and everything else in the tank. You will need to wash each piece of rock or gravel with great care to minimize bacteria, debris and germ buildup.

Rocks that are low to no maintenance to keep are the best. These rocks are durable and resistant to impact. Stones and rocks that are porous are much more difficult to clean than the ones with smooth surfaces. Larger pieces are also easier than smaller rocks. Think about the maintenance it takes to keep things clean before you make your decision.

How to Care for, Wash and Clean Aquarium Rocks

We mentioned the importance of cleaning and washing your aquarium rocks when you first get them and periodically, so we’re going to show you how! Let’s first address either gravel or pebble aquarium beds. The smaller sizes of these rocks can make it easy if you have all the tools you need.

Related: The Aquarium Cleaning Guide

Start off by preparing an extra bucket and a sieve. The bucket and sieve size can vary depending on how big your tank is and how much gravel or how many rocks you need to clean. Also, make sure the sieve can sit on top of the bucket seamlessly. You are basically making yourself a filter system to clean the rocks.

Place the bucket on the ground with the sieve sitting securely on top. Start pouring the gravel into the sieve little by little. Don’t pour the whole lot in but just enough to fill half the sieve. This is because you need to give yourself enough room to pour in water and to swirl and clean the rocks.

Start pouring water slowly into the sieve on top of the gravel while shaking and swirling your fingers to separate the gravel and rocks. Keep repeating this step until the water going into the bucket runs clear. Remove the clean gravel or rocks from the sieve and place it somewhere secure. If you have already finished cleaning the tank, it can go back inside. Keep doing the above steps until you get through all the gravel and rocks.

If you larger pebble rocks that don’t require a sieve, you can opt for a tray instead. The steps are relatively the same, just pick out a portion of the rocks, put them into the tray, and run water over them while turning them over and over in your palms until the water runs clear. Rocks with non-porous surfaces are easier to clean, and taking these steps is enough.

Make sure you do not add any soap or cleaning solutions into the water unless they are specifically meant for cleaning the fish tank and rocks.

coral reef sea blue water aquarium

If you have larger and porous rocks, then the steps to cleaning them are a bit more difficult. If you notice surface residues such as algae buildup or calcium buildup, then break out an old toothbrush, small cleaning brush or a sponge.

You need a separate bucket to house the rocks while you’re cleaning. Some aquarists say you need bleach for the tougher-to-remove surface residues, but we won’t suggest that unless you need some heavy duty cleaning. Adding any type of chemical to your cleaning water can pose unseen risks to your fish.

Fill the bucket up with clean freshwater and soak all the rocks inside for at least a quarter of an hour. If you have a cleaning solution meant for this type of cleaning, then add it into the bucket. After 15 minutes, ready your sponge or brush and scrub each individual rock separately. Try not to put the clean rocks back into the same bucket with the dirty unwashed rocks, so prepare an extra bucket or tray to house them in the meantime.

Make sure to get into every crack, crevice or pore to rid the rocks of buildup. When you have finished scrubbing all the rocks, soak them once again for 15 minutes. Do not add in the cleaning solution again if you did before. After 15 minutes are up, we would suggest giving them a good rinse under running water again just for good measure.

Make sure you let all the pieces of the rocks dry completely before putting them back in the tank. Because this could take a while, you need to have a secondary tank prepared to house your fish for the time being.

The above are the cleaning steps for algae, but calcium buildup in your aquarium rocks requires a different routine. Calcium buildup is much more difficult to clean and might require some solutions such as bleach or vinegar, but depending on the type of fish you have, these solutions can be harmful if not properly cleaned. Just to be sure, we would suggest asking your trusted vet.

For cleaning off calcium buildup, you will need to soak your rocks in the solution for a good couple of hours. Make sure you submerge the rocks completely so all the calcium is soaked through. When time is up, take your brush or sponge and start scrubbing. You will know your efforts are successful if the crusty layer starts to come off. Your goal is to feel the smooth surface of the rocks again.

When you are done cleaning each piece, run them under clean water again just to get all the solution off of the rocks. Let each piece dry thoroughly before placing them back in the tank.

How do I Know the Rocks are Safe?

It can be daunting when placing the rocks back in the tank if you don’t know how good of a job you cleaned. Just to make sure everything is safe, you can do an easy at-home test. What you need includes water pH test kits and a clean tray. Soak the rocks for good measure before you conduct this test.

Soak the rocks in the tray for a day and then conduct the test. If the rocks are in the optimal pH level range, you know for sure it is safe to place them back in the tank.

Frequently Asked Questions

Can I use outside rocks for my aquarium?

You can use outside rocks for your aquarium in some rare cases, but in general, it is almost always advised against. Outside rocks are unclean and are packed full of bacteria and germs. Once placed into your tank, it will drastically alter the environment. You also won’t know the type of microorganisms that may inhabit the crevices of each stone. Some may prove to be detrimental to your fish’s health. It’s always a safer bet to use rocks that are specially treated for your aquarium.

What are the differences between freshwater aquarium rocks and saltwater rocks?

The requirements for saltwater and freshwater fish are different, therefore the rocks you use in saltwater tanks won’t work in a freshwater aquarium. Rocks for freshwater aquariums should not affect the water environment while rocks for saltwater tanks are meant to preserve and maintain the right water conditions. When purchasing rocks for your fish tanks, they should be clearly listed and mention which type of tanks they are suited for.

What rocks are safe for a freshwater aquarium?

Lava rock, slate rock, dragon stone or mountain stone, and even petrified wood are safe for a freshwater aquarium. These types of rocks will not alter the state of the water and can exist in harmony with freshwater fish.

Do I Need to Clean Aquarium Rocks?

Some people might think a good rinse on occasion is enough to maintain the conditions of their aquarium rocks. However, this doesn’t address unseen bacteria buildup, algae and calcium residue as well. If left for a long time, they can have a detrimental impact on the water conditions in your aquarium and hurt your fish. So yes, you need to clean your aquarium rocks.

How Often Should I Clean My Aquarium Rocks?

The more often you clean your aquarium rocks the better. However, this can be difficult if you don’t clean your entire tank, especially if you have pebble rocks or gravel. A fish tank is best cleaned every two weeks or so, but minimal maintenance should be done weekly. By minimal maintenance, we mean slight water changes and cleaning up leftover fish food.

Can I Boil the Rocks to Clean Them for My Freshwater Tank?

There are some aquarists that advise boiling your rocks when you are preparing for your aquarium. A good boil at about 10-15 minutes will kill bacteria and certain pathogens. This will also help to disinfect the rocks. However, some fish species are very sensitive to temperature changes, so make sure your rocks have completely cooled before placing them back in the tank.

Conclusion

Aquarium rocks are an essential part to the aesthetics of a fish tank. The right ones can elevate the appearance of your miniature marine habitat and can also preserve the water conditions. Choosing the right one is important for the health and safety of your fish. If you follow our buyer’s guide, you will find safe solutions that will be great additions to your aquarium. Just remember to clean the rocks thoroughly before adding them to the tank unless they are stated as prewashed.

Our favorite type is dragon stone for its beautiful look that adds a touch of luxury to your tank. What many people don’t know is that dragon stone, or dragons, are viewed as lucky symbols in Asian culture and are known as protectors. So adding some dragon stone to your tank can protect your fish and by extension, your household.

Expert Tip

We would advise against leaning the rocks on the side of your aquarium. Doing so can destabilize your fish tank and run the risk of cracking your tank if your fish knock them over. This is also why stabilizing the rocks in your tank is important. You can hold them together with epoxy putty that is non-toxic.

Did You Know?

Don’t overstuff your tank. You still need to give your fish enough free space to relax and explore unless you just have a decorative tank. Keep most of the rocks and other plant substrate gathered in the center. You can also consider stacking the rocks and moving upwards instead of spreading them out side by side. The key is the placement of the rocks to not limit space.

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