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10 Best Rocks For Freshwater Aquariums | Safe Stones Guide

Choosing the best rocks for your freshwater aquarium can sometimes be a daunting task.

On the one hand, you want to make sure the tank is beautiful to look at. On the other hand, you want to make sure you aren’t adding rocks that could potentially upset your delicate ecosystem.

Most people don’t realize that the rocks you put into the aquarium can have negative impacts on your fish and plants, either.

Freshwater tanks are considered “soft water” environments and putting the wrong type of rocks could make it incredibly uncomfortable for your fish.

Maintaining the hardness and pH level in your water, especially after introducing new rocks to the system, can be challenging to do. Some of those rocks contain calcium while others contain salt, two ingredients that can dramatically throw off balance in your water.

One option to offset the swings in pH level is to use wood that helps soften the water again, but this creates a situation where you’re always teetering back and forth.

 To make sure you aren’t upsetting the delicate ecosystem you’ve worked so hard to build and maintain, we have put together a list of aquarium-safe rocks. Adding these into your tank will help beautify your tank instead of making it harder to maintain.
Very Natural Looking - High Value
  • Perfect For Home Decor And A Creative Interior And Exterior Design
  • Easy On The Feet As There Are No Sharp Edges
  • Used In Flower And Garden Beds And On Walkways For Erosion Control
​​Beautiful Stones - Best Value
  • Awesome Quality And Variety
  • Non-Toxic To Your Fish, Plants, Or Other Animals In The Tank
  • Creatively Shaped To Give The Most Distinctive Look Possible
Great Rock - Best Choice
  • “Out Of This World” Look.
  • Easy To Pile, Shape, And Mold Onto Each Other
  • Very Easy To Aquascape
Great Quality - Recommended
  • Perfect For Creating Walkways, Benches, Steps, Archways, Caverns And Ground Cover
  • Use In Home Decor In Bowls And Vases And As Ground Cover For Indoor Plants
  • Perfect Size And Shape For Rock Painting
Safe and Non-Toxic - High Quality
  • Provides The Essentials Required For Proper Coral Growth
  • Great Mix That Contains Higher Levels Of Magnesium, Calcium, And Strontium
  • Very Mild Blend That Has Shown To Be Safe For Invertebrates And Corals
Incredibly Unique - Best Choice
  • Add Natural Beauty To Your Aquarium Or Terrarium With This Stunning Rockwork
  • Provide A Haven For Your Smaller Fish
  • Add An Incredibly Appealing Structure To Your Tank
Durable And Long Lasting - High Quality
  • High Quality, Low Maintenance: Durable, Long-Lasting And Cost Effective
  • Great In Soil To Retain Moisture For Plants And Also Work Well As An Addition To Aquariums And Ponds
  • Easy To Stack And Build Into New Designs
Decent Rock - Best Value
  • Rapidly Adapts To Live Environment & Will Not Affect The Cycling Of Your Tank
  • Perfect For Coral Farming, Culturing Live Rocks & Growing Live Coral
  • Provide A Great Place For Algae Eaters To Feed And Thrive
Very Realistic Looking - Recommended
  • Eco-Friendly, And Won’t Displace Or Reduce The Amount Of Water In Your Aquarium
  • Molded With Care And Hand-Glazed To An Eye-Catching, Natural Look Of Perfection
  • Natural To Set Up, Stack, And Move Around
High Quality Granite - High Quality
  • Provides Visual Interest For You And Your Fish
  • Made Of Safe Durable Resin, This Aquarium Decoration Is Safe For Use In Both Freshwater And Saltwater Aquariums
  • Make Perfect Hiding Hubs For Your Smaller Fish

10 Best Aquarium Safe Rocks - In-Depth List

After scouring through hundreds of different rocks, uncovering what they’re made of, how they affect soft water environments, and whether or not they’re safe for fish, we have listed 10 of the best aquarium safe rocks below.

Highlights

  • perfect for home decor and a creative interior and exterior design
  • easy on the feet as there are no sharp edges
  • used in flower and garden beds and on walkways for erosion control

Typically, we wouldn’t recommend adding river rock to your tank. It can transmit bacteria that isn’t native to your ecosystem and cause a lot of damage to your fish.

However, aquarium river rock is some of the most beautiful stones you can add to your tank.

Royal Imports river pebbles are one of the few brands of river rocks we would recommend using. They not only help your tank appear more attractive, but they also help create a system that your fish and invertebrates can thrive inside.

The most common use for these river rocks is tying down plants and giving your tank hardbottom sections for fish that prefer them over sandy bottoms. The stones vary in size, shape, and color, which helps add a unique flair to your tank.

Each of the stones in the Royal Imports bag is rolled and tumbled, giving them a polished look that remains rugged. This process helps bring out the colors and luster, letting the undertones shine through when water hits them.

If you are looking for a natural appeal, these river rocks contain the most natural colors you will find. Browns, greys, blacks, and tans make up the entire range.

While these river rocks are cleaned and tumbled before arriving at your doorstep, you do still want to make sure you are cleaning them thoroughly to remove any small debris.

Pro Tip


Pros

  • Non-toxic for all species of fish in your tank.
  • The natural colors help increase the decorative appeal in your tank.
  • These rocks provide a great alternative to softer, sandy bottoms.
  • The rocks are shaped and sized perfectly to help with drainage.

Cons

  • May give algae a surface to bloom on if not kept in check.
  • The tumbling process removes the shine and luster.

2. Pisces Seiryu Rocks - Beautiful Stones

Highlights

  • Awesome quality and variety
  • Non-toxic to your fish, plants, or other animals in the tank
  • creatively shaped to give the most distinctive look possible

When you want to add visual appeal to your freshwater aquarium, the Pisces Seiryu rocks are a great way to do it. These are a hardscape rock that is humanmade to help provide a realistic look, feel, and weight.

If you are familiar with Amano or Iwagumi aquascaping, you understand the appeal.

Since these rocks are humanmade, you do not need to worry about them being toxic to your fish, plants, or other animals in the tank. The all-natural stones are great for shrimps and other plants and do not modify your water’s chemistry.

 Creating a natural backdrop in your tank is easy to do with relatively low maintenance. Each rock is creatively shaped to give the most distinctive look possible. The stones do not drift when they are placed near your pump as some other humanmade rocks do.

Pro Tip


Pros

  • Safe for all species of fish, plants, and invertebrates.
  • The humanmade rocks are incredibly detailed in design.
  • The unique size, shape, and style add a distinctive appeal to your tank.
  • These rocks serve as a fantastic centerpiece in every aquascape.

Cons

  • The rocks can be substantial and jagged; take care while placing them in glass tanks.

Highlights

  • “out of this world” look.
  • Easy to pile, shape, and mold onto each other
  • very easy to aquascape

These rocks are widely regarded as some of the best rocks you can put in your aquarium.

They are a porous rock, so you don’t have to use toxic or harmful chemicals to help hold them together or keep them in place while you are stacking them. Compared to other rocks, these have been said to have an “out of this world” look.

The natural colors and large sizes can be broken down to expose the undertones and create smaller stones you can use as accents. It’s easy to create an island structure with these rocks.

One of the most significant selling points of Atlantic Coral Rocks is their price range. They are far cheaper than many other types we’ve seen. With aquascaping being such an expensive hobby, save money where you can!

While these rocks do look amazing in your tank and come alive underneath an LED light, they serve another beneficial purpose. Healthy bacteria can grow and thrive in the porous surface, and your fish will learn to feed on them in between your scheduled feeding times.

Pro Tip


Pros

  • Real rocks straight from the Atlantic ocean.
  • Great value for the price you’re paying.
  • Easy to pile, shape, and mold onto each other.
  • A wide variety of sizes and shapes makes aquascaping easy.

Cons

  • You will need to clean the sand out of the rocks before using them.
  • The rocks can be brittle so take care while placing them.

4.  Natural Stone SlateGreat Quality

Highlights

  • Perfect for creating walkways, benches, steps, archways, caverns And ground cover
  • Use in home decor in bowls and vases and as ground cover for indoor plants
  •  Perfect size and shape for rock painting

One of the coolest decorations you can add to your tank is natural slate stones.

They double down as both a decorative addition to your tank but also a great way to keep your plants firmly rooted. When your plants are close to the inflow of your pump, they tend to move around. Flat slate stones keep the roots firmly planted while the tops of your plants can flow.

These are a natural grey color and become darker in color as they spend time in the water. They do not leech calcium or throw off the pH levels in your tank, so you do not have to worry about affecting the health of your fish by adding them into your aquascape.

Each slate stone can be broken, shaped, and molded to fit exactly what you’re going for. You can use them to create hideouts for smaller fish or stack them to create a water feature that uses your pump’s inflow to create tranquil background noise.

Pro Tip


Pros

  • These are ideal for keeping plants rooted in place.
  • They can be stacked to create hideouts or water features.
  • The slate stones are natural to break and shape, as needed.
  • Slate stones help hold heat and resist algae buildup.

Cons

  • Slate stones can be incredibly sharp, potentially damaging glass tanks.
  • These smaller stones are not ideal for large aquascapes.

5. VORCOOL Aquarium Sea Rock CaveSafe And Non-Toxic

Highlights

  • Safe and non toxic for use in both freshwater and saltwater.
  • perfect size decoration for any tank
  • promote healthy bacteria growth that those same smaller fish can feed on

VORCOOL is a brand name that has been around aquarists and aquascaping for years.

The VORCOOL Sea Rock Cave is an excellent addition to any tank. Known for producing only the highest-quality decorations, you don’t have to worry about introducing harmful toxins to your aquarium as you do with knockoff brands.

This cave is a great way to help your smaller species hide and tuck away while also helping promote healthy bacteria growth that those same smaller fish can feed on.

However, with the beauty of the rock cave comes a single caveat: the edges can be sharp.

The molding process has been known to leave a few rough edges here and there so you will want to sand them down before you install it into your aquarium. These sharp edges can hurt your fish.

You will also want to make sure you scrub the cave with dish detergent or another mild detergent to help remove some of the release agents that are used during the molding process.

While the release agent isn’t harmful, it does have a pungent odor that can be offputting to some people.

Pro Tip


Pros

  • Perfect hideout for Coryfish and other bottom-dwellers.
  • It provides a dark area for healthy bacteria to flourish.
  • Adds a natural look to your aquarium.
  • It helps your frogs and turtles bask and get fresh air.

Cons

  • You will need to scrub the release agent off the cave before installing it.
  • You may need to sand down rough edges on the cave.

6. SevenSeaSupply Ohko Dragon Stonesincredibly unique

Highlights

  • Add natural beauty to your aquarium or terrarium with this stunning rockwork
  • provide a haven for your smaller fish
  • add an incredibly appealing structure to your tank

SevenSeaSupply is another well-known company in the aquascaping industry.

The SevenSeaSupply Ohko Dragon Stones are an incredibly unique addition to any tank, too.

These natural stones help provide a haven for your smaller fish, giving them a structure to huddle around and relieve stress. The design also makes them incredibly visually appealing.

The rocks have naturally occurring creaks, cracks, and crevices for your fish to hide in and around, and to help promote healthy bacteria growth.

It is worth noting that these are humanmade stones. While they are natural materials, you will need to take care and wash them before installing them into your tank. You don’t have to worry about harmful chemicals, but some customers have reported a film reaching the surface of the water after installing the Dragon Stones.

Pro Tip


Pros

  • The Dragon Stones add an incredibly appealing structure to your tank.
  • The cracks and crevices are perfect hideouts for smaller species.
  • The natural browns, tans, and greys have an exotic look.
  • The package comes with rocks of all shapes, sizes, and colors.

Cons

  • These Dragon Stones are fragile, so you must take care while placing them.
  • You will want to wash the dust and debris from them before installing them.

7. American Fireglass Black Lava RockDurable and long Lasting

Highlights

  • High quality, low maintenance: durable, long-lasting and cost effective
  • great in soil to retain moisture for plants and also work well as an addition to aquariums and ponds
  • easy to stack and build into new designs

Finding high-quality lava rock that is safe to use in your aquarium can be hard to do. The American Fireglass company’s Black Lava Rocks are the exception to that rule.

Each rock is a naturally-occurring stone, nothing humanmade here. They are relatively low maintenance and have been proven to withstand the test of time in tanks around the world.

One of the most significant selling points is the dark, deep black color that helps offset the more natural colors in your tank. You can use the lava rocks to hold down plants or create caves and nests where your smaller species can hideout.

Pro Tip


Pros

  • Each rock is pre-certified as all-natural; nothing humanmade.
  • The rocks will withstand being in your tank for years.
  • The porous rocks help aid healthy bacteria growth.
  • These are easy to stack and build into new designs.

Cons

  • You will need to pay attention to algae growth when you use lava rocks.
  • You will need to wash the dust off the rocks before using them in your tank.
  • Some edges can be sharp, so you’ll need to take care of glass aquariums.

Highlights

  • Rapidly adapts to live environment & Will not affect the cycling of your tank
  • Perfect for Coral Farming, Culturing Live Rocks & Growing Live Coral
  • provide a great place for algae eaters to feed and thrive

Finding good coral rocks to use in your freshwater tank is nearly impossible to do. Unless you have access to a live coral environment near you, these can be impossible to source.

Nature’s Ocean knows how much aquarists love using coral in their freshwater tanks and started sourcing base coral rocks for reselling. This is a larger rock, in the 12-inch size range, so you’ll want to keep that in mind before you purchase.

Each piece of coral can be broken down to create a very specific aquascape. The coral rocks do not introduce harmful chemicals to your water but do have the potential of leeching calcium. If you use them, you’ll want to keep an eye on your pH and hardness levels.

The naturally occurring holes and crevices allow healthy bacteria to grow and give your algae eaters plenty of places to pick apart.

Pro Tip


Pros

  • Each of these coral rocks is bio-film free and safe for freshwater use.
  • The rocks provide a great place for algae eaters to feed and thrive.
  • The larger rocks can be broken down into smaller chunks.
  • Nature’s Ocean helps protect live coral reefs and farming.

Cons

  • You will need to clean these before using them thoroughly.
  • These coral rocks can be expensive compared to other stones we’ve featured.

9. Underwater Galleries Cichlid Rocks - Very Realistic Looking

Highlights

  • Eco-friendly, and won’t displace or reduce the amount of water in your aquarium
  • Molded with care and hand-glazed to an eye-catching, natural look of perfection
  • natural to set up, stack, and move around

Cichlid Rocks from Underwater Galleries are another unique stone you can add to your tank.

They provide large caves for your smaller species to hide in and for, as the name suggests, Cichlids to breed in. The darker caverns are also great for helping promote healthy bacteria growth that your algae eaters can feast on.

The eco-friendly design of these stones is what helps set them apart. They do not displace as much water as other stones, and each stone is hand-glazed. The construction helps maintain a natural appearance that you can’t help but pay attention to.

Each package comes with six large stones and four medium stones, all with varying styles. The smaller rocks feature 1-inch openings while the larger stones feature up to 2-inch openings.

While the larger stones do allow your smaller fish to move in and hide, the smaller rocks make it harder for fish to get in and out. That means you will need to pay attention to keeping them clean, in case of algae bloom breaks out.

Pro Tip


Pros

  • These stones do not displace a large volume of water.
  • The stones are natural to set up, stack, and move around.
  • Each package includes a wide variety of shapes and sizes.
  • The stones are constructed from hand-glazed high-quality ceramic.

Cons

  • The stones are not as large as they appear in pictures.
  • The interior surface is uneven and may contain sharp edges.

10. Penn Plax Stones - High Quality Granite

Highlights

  • provides visual interest for you and your fish
  • Made of safe durable resin, this aquarium decoration is safe for use in both freshwater and saltwater aquariums
  • make perfect hiding hubs for your smaller fish

Finally, we have Penn Plax Stones. These are another unique stone that offers plenty of hideouts for your smaller (and larger) fish, as well as the ability to stack the rocks to create customized aquascapes.

Each stone is crafted to look like a real piece of granite that has been molded and shaped by flowing water for generations. Larger stones feature a flat surface to help make stacking easier to do.

A ton of customers has reported that these stones do not hold algae-like many other porous stones do, because of the materials they are constructed from.

 These replica stones are great for Cichlid tanks and Betta tanks, as well as tanks where you have schools of smaller fish congregating.

Pro Tip


Pros

  • Each stone is a high-quality granite replica.
  • The stones are molded from solid resin; safe to use in your tank.
  • These make perfect hiding hubs for your smaller fish.
  • The stones can be used in both freshwater and saltwater tanks.

Cons

  • The stones can be somewhat fragile. Take care while placing them.

What Are Unsafe Rocks For Aquariums?

There are a handful of rocks that are known to cause problems in freshwater tanks:

  • Coal
  • Dolomite
  • Limestone
  • Sandstone
  • Pyrite

Each of these stones will change your water’s makeup, causing you to perform maintenance more often. Some will even leech harmful toxins into the water.

How To Make Aquarium Rocks Safe

Before you put any rocks into your aquarium, you want to make sure you spend time scrubbing them with a nylon-wire brush. Using a light detergent, clean the stones until you are sure they are free from dust, debris, and any potential bacteria that may have clung on.

How To Set Up Rocks In An Aquarium

Because some rocks have sharp, jagged edges, you will want to take care while you are placing them into your tank. Make sure there is a substrate underneath them and that the rocks are not able to tip over.

With the pressure inside of your tank, it is easier to puncture the glass from the inside than it is the outside. A falling rock can easily crack the glass! Especially if the stone has a sharp edge!

Where To Find Rocks For An Aquarium

If you are going into the wild to find rocks for your aquarium, make sure that you aren’t taking any from the list of unsafe rocks. As long as you have verified that they are safe to use with your fish, take precautions in scrubbing them properly.

How To Prepare Rocks For Your Aquarium

Before you put the rocks in your tank, you may want to soak them in an alcohol solution to help kill any bacteria that came from the area where you took them. If you are buying pre-packaged rocks, this isn’t as big of a deal.

What Are The Best Rocks For Freshwater Aquariums?

This is a personal decision that is going to come down to what you want from your aquascape.

Some aquarists prefer a natural-looking aquascape while others may want a more exotic look.

As long as the rocks are on our safe list, or recommended by other freshwater tank owners, you can assume that they are safe to use. Then, choosing the best rocks for your freshwater aquarium comes down to what you think looks the best and gives your fish a good home!

Affiliate links & Images from Amazon Product Advertising API. Last update on 2019-10-18.

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