Your Guide on the Best Rocks for Freshwater Aquarium

Published on August 12, 2019
Your Guide on the Best Rocks for Freshwater Aquarium

What makes an underwater landscape a breathtaking sight?  Aside from the fish and aquatic plants, everything in it exhibits a role to fascinate the onlookers.

The hardscape like woods and aquascaping rocks are effective decorations that can replicate an environment closer to the habitat where fish and plants have grown accustomed with.

An aquarium layout that looks natural must include a creative hardscape of gravel, tree roots,  driftwoods and rocks other than fish and plants.

Aquarium rocks can dramatize scenery like a plateau or a mountain, or cave for hiding. Other than those, they also serve many purposes in your ecosystem like home for algae and helpful bacteria.

This article will make you realize why rockscape is an essential aspect of beautifying your aquarium. This serves as your guide for endless fish tank gravel ideas.

Let your fish explore, feel safe and happy by adding the best rock for freshwater aquarium.

The Need for Freshwater Aquarium Rocks

lava rock aquarium

If you are a newbie to the Aquascaping hobby, you often wonder how to prepare rocks for aquarium. With the unlimited number of stones, you can decorate your planted tank also in endless ways; your imagination is your limit. But why do you have to? These are the reasons: -

  1. Aesthetic appeal.
  2. Rocks can replicate an ideal ecosystem closer to the Biotope of your fish and plants.
  3. Calcareous rocks raise the level of pH of the water and make it hard like marine habitat.
  4. They serve as areas for hiding, playing, and breeding for fish.
  5. Algae and other microorganisms will cling to the rocks. These are food sources for some of your tank’s inhabitants.
  6. Rocks provide a convenient spot for some good bacteria and microorganisms to nitrify and create its territory. This wards off toxins like ammonia and nitrites from tanks.
  7. Rocks can make a miniature mountain and plateau for an eye-capturing design.
  8. The right positioning of rocks has an excellent effect from the LED Lights. It can serve as a shade or can turn your tank into a multicolored sight.
  9. As your rock ages, its color changes too, so we can say rocks provide seasons.
  10. An aquarium embellished with plants and rockscape provides a haven to your fish. They’ll be happy, safer, and feeling home.

Type of Rocks Suitable for Freshwater Aquarium

aquascaping rock

Let’s refresh our Geology lessons when we were in High School. To understand everything about aquascaping rocks*, we need to trace the roots of them all.

Igneous rocks

This results from crystallization or surfacing of molten rocks from the core of the Earth. These rocks can be basalt, dolerite, or gabbro, which are all beautiful to include in an aquarium.

Sedimentary rocks

This is from the bits and pieces of sediment deposits that have compressed together through time. It cycles over and over and forms in layers, like what we see in the images of sedimentary rocks. It includes sandstone, limestone, marl, breccia, conglomerate, and shale.

Metamorphic rocks

This category of stones varies in appearance as they change because of heat exposure and pressure. Dolomite, marble, schist, quartzite, hornfels, slate, gneiss and phyllite are all the types of metamorphic rocks.

All these natural rocks can decorate any aquarium, but it still depends on the biotype you keep in your tank. Some rocks are appropriate only for marine, coral, and reef tanks (saltwater).

Freshwater aquariums require soft water. Adding intrusive rocks can turn the water hard, which is not suitable for the fish.

What type is the best rock for a freshwater aquarium?

Those that won’t affect the hardness or pH of the water are the ones I will recommend. Inert rocks are the best types of freshwater aquarium rocks*.

Stay away from calcareous rocks because these contain Calcium that might boost the hardness level and pH level in the water.

Avoid geodes, shells, marble, limestone, dolomite, and crushed coral in tanks. A reasonable exception is including calcareous rocks (with no salt contents).

This is only when you keep African Cichlids and other freshwater fish that prefer hard water. Just add a clean wood in the tank to make the water soft.

Lava Rocks

lava rock aquascape

I don't think you need an introduction on what lava rock is, right?

Just a fun fact, there are 700 types of lava rock that exist today.

What are the characteristics of a Lava Rock?

  1. Lava rocks can be gray or black, but the most popular is the red-orange one.
  2. Since they came from cooled volcanic lava, they are hardened enough to become long-lasting.
  3. Lava rocks can be home to colonies of beneficial bacteria because they are porous.
  4. Most of these rocks have one or two holes where fish can swim through, hide, and play.
  5. This rock makes a perfect lava rock aquarium* where you integrate something that came from nature.

What are the variations of Lava Rocks?


It is a form of sedimentary rock that comprised clay, calcite, and quartz. It comes in black, purple or grey, and is thin and long in appearance.

The rock has aged for hundreds of years that make it durable.  In aquascape, these rocks make perfect plateaus. They are accessible in any LFS in pre-sterilized stature.


This metamorphic rock comprises fine-grained Shale that transformed into clay, ash, and quarts. They are more than a hundred years old, just like the Shale because they came from it.

You can find Slate in color variations of green, purple, gray, and blue which can make a plateau layout more eye-catching. This is a perfect addition to your lava rock aquarium, either in a saltwater or freshwater tank.


This igneous rock took its form through molten volcanic lava that got hardened. The color is very natural, dark, and greys if not black. It is dense, durable, and comes in a variety of shapes and sizes.

Aquarists recommend this rock because it won’t cause pH buffering, so it is safe for both fresh and saltwater. You may be lucky finding it in nature, but they are available in your local fish store.


When you see a transparent, gem-like crystal stone, they are quartz rocks. Its lustrous appearance adds an extra glow in your aquarium, more so from LED lights effects.

They resemble precious stones like diamonds, amethysts, topaz, etc. Colors can be purple, yellow, pink, white, or black. These rocks are inert, so it won’t alter the hardness and pH level of your water.

Are plastic rocks safe for decoration?

One of the many fish tank gravel ideas is by adding plastic rocks for a scenic touch. These are plastic-made or from polyresin and handcrafted to look like real rocks.

They come in assorted colors and also in gravel form. Place them anywhere you want in the tank and let your imagination run. These are safe for fish, in freshwater or any water salinity.

The only downside of it is that you cannot get the natural rock-look because they are a pure imitation. There are no beneficial properties from it, although they do not affect the pH of the water.

Guidelines in Selecting Aquascaping Rocks

In selecting the best rock for a freshwater aquarium consider the appearance, cleanliness, characteristics, safety, and value for the money.

You can buy from your LFS, and the store's fish advisor could share you some tips coming from the experienced. You can also buy online but do some research first, read reviews, and look for the high-rating ones.

Appearance (for visual appeal)

Check for the crevices or holes because these can provide recreation to your fish. They swim through it, play and swim around. Likewise, these holes serve as dwelling or resting places, hiding, or breeding areas.

Measure only what you need; do not over-decorate to avoid congestion and discomfort. These rocks feel like home for a lot of your tank’s occupants because it replicates their natural habitat.

Red, purple and pink colors are appealing for aquascaping rocks. These signify good health and maturity like coralline algae coloration, which fish will adore.

Beneficial Characteristics

A lot of experienced aquarists settle for what benefits they can get when decorating with rocks and stones. They want these to be home for beneficial bacteria colonies which counteract the rise of ammonia and nitrites in the water.

They do not just provide home, hiding, breeding places for fish, but rocks can invite algae and other microorganisms which are essential food sources of other pet fish species.

Do not choose rocks that are too heavy for your tank like granites. They are fantastic inert rocks and can be great for aquascaping, but they’re dense and large.

Some rocks can change the level of pH and hardness of the water, so know the water parameter needs of all the fish and plants housed in the aquarium.


Avoid choosing rocks that came from populated areas for they can be dirty or slimy with all the toxins and harmful bacteria.

It is fun to collect rocks from rivers and other bodies of water, but you don’t need to. You might catch those with deadly black algae.

A lot of aquascaping rocks for sale are pre-sterile and ready to use. If you will cure them yourself, allow 30 minutes of boiling time, wipe it dry and let it rest a while before putting in the tank.


Watch for metal contents of the rocks because they can pose dangers to all the living organisms in your tank. Do not buy rocks with damaged, sharp edges, and alterations for they will deteriorate soon and can pose a danger to your pet fish.

A thorough rock examination will help you look for signs of germs and harmful creatures. Avoid choosing foul-smelling rocks like rotten or fishy for this could mean that stones aren't yet cured. If they don’t look right, leave them.

Consult the authority if you need help. Your LFS is the best hub for rocks and stones for they know how to clean and sterilize them before selling.


Know your budget and adjust your options. Rocks that came from nature fetched a higher rate than the imitations.

If you prioritize value, do not go for just the looks but both looks and benefits. Do not compromise low price from quality.

This could be a surprising investment for you, other than just a hobby. In the end, you will know why.

The 7 Best Rocks for Freshwater Aquarium

Seiryu StoneRock

These famous blueish-grey rocks by Aquascaping Stone are a fast-selling best rock for freshwater aquarium because they came from all-natural stones. They craft these hardscape creations to perfection to exude a realistic view.

They looked like small rock formations sculpted in various sizes and shapes. You can place it in your tank without worrying that they may drift because they can sink in an instant.

Most of these stones comprised deep cuts, sharp jagged edges, and crevices within. Seiryu Stones have a presence of calcite veins within their layers, creating a pleasant contrast from its vibrant blue and grey hues to its white veins stripes.

You can find them at Iwagumi and Amano types of aquascaping. These rocks can form a perfect backdrop for aquascaping themes like bonsai garden, biotope, terrarium, and other conventional Japanese garden themes.

Seiryu stones won’t change the chemistry of your water, but if you put more, it will raise GH and pH levels. If this happens, put driftwood or RO water to counteract such an effect.

They are still safe for your fish, plants, and invertebrates because the rocks are not toxic. A stunning variation of these rocks serves as perfect hiding hub and dwelling places for your pets. You decorate with benefits along the side.

These stones come with grains for stuffing moss and plants into.  Mosses create stunning scenery like a peaceful Zen for your tank inhabitants.


  • Safe and non-toxic
  • Premium quality for the money
  • More variations for embellishment
  • Shapes come in unique crevices, holes, and texture
  • You and get a 20-lb box of pre-selected stone mix per pack


  • Natural stones look untidy
  • Not lightweight

Carib Sea ACS00370 South Sea Base Rock for Aquarium

Carib Sea ACS00370 South Sea Base Rock has more to offer other than just the looks. They formed its gorgeous shape from erosion and weather processes.

Transform your tank into a lava rock aquarium that resembles a natural ocean floor. The rock has more structures than the others; therefore, aquarists include it in their fish tank gravel ideas.

Carib Sea Base Rock has a void space of 50% porosity. It means water can flow through it, causing no damage, thus making it long-lasting.

Those crannies and little nooks in the rocks are a nitrifying place for good bacteria. Use it as a base or as an effective alternative to live rocks.

They are safe for both freshwater and saltwater tanks. However, the rocks require a higher pH level for freshwater because of its calcium carbonate content, which they gained from coral reef grounds.

These South Sea Base Rocks come in a 40-lb pack that varies in sizes and shapes. If you want a larger rock design, you can attach one from the other using a safe aquarium glue.


  • Porous at 50% void space
  • Variety of sizes, shapes, and structures
  • Can be an alternative to live rocks
  • Safe for reptiles
  • A product of the USA


  • It needs a higher pH level for the freshwater tank because these rocks have calcium carbonate content, which is potent only to higher pH.

Underwater Galleries Cichlid Stones

Underwater Galleries Cichlid Stones are human-made river rocks for a freshwater aquarium. They are large and has roomy interiors suitable for tanks inhabitants to explore, hide, and swim through.

This is a useful breeding place for it can provide shielding niches for the fry and shade against the light.

The rocks are eco-friendly and lightweight so that they won’t displace or minimize water in the aquarium.

These are fancy, hand-glazed faux rocks. They crafted these stones with a lot of skills for a more natural look.

These Cichlid rocks come with 4 or 6 large stones in three different versions. Clean the rocks (no brushing) to preserve the textures and colors.

Despite a bigger opening for the larger rocks, the smaller ones have only an inch of an opening which justified their being natural.

Your growing fish might not fit into the opening, the more so, the bigger ones. They might push over or block the stone’s opening. Anyway. These rocks are lovely aquascaping rocks decorations if they cannot serve their primary purpose.


  • Eco-friendly, user-friendly
  • No considerable amount of water displacement
  • Lightweight can move the stones with ease
  • Rocks have several holes, crevices, caves
  • High-quality ceramic


  • Not as huge as in the advertisement
  • Uneven cave surfaces

Natural Slate Stone

If you are thinking of some fresh fish tank gravel ideas, these natural slate stones are a great pick. It’s a perfect embellishment not only for aquascaping but also in your home garden.

It’s practical to choose Slate stones for any crafty ideas, not just for aquariums.

Because they come in a variety of shapes and sizes, you can use the larger ones to form a hill, cave, plateau, cavern, railways,  dollhouses, archways, etc. The smaller ones can make some lovely backdrop pieces.

Attach the stones in alternates, stack them up as stone shelves for your miniature bonsai plants. Hardscaping hobby entails creativity because endless possibilities are using the Natural Slate Stones.

I always relax looking at my indoor plants where I covered them with these rocks. It’s refreshing to just put them in my vases and plant bowls for a natural touch, but I know they’re best aquascaping rocks, so I won’t miss outputting these rocks in my 100-gallon Biotope tank.

These stones have a natural grey coloration which grew dark when drenched. Make them darker by using a sealant and a clear finish. But, for me, I prefer its natural characteristics.

Before its use, wash the stones thoroughly although they are pre-sterile when sold. Use safe aquarium glue to attach the small pieces if you opt to put them in your tank.


  • Ideal for any creative structures
  • Excellent fish tank gravel ideas*
  • Best for vivariums and terrariums
  • Great value for the money
  • Variety of sizes and shapes
  • For embellishment of home vases, pots, and bowls
  • Perfect for rock painting
  • Can hold heat for reptiles


  • The package contains small broken bits with sharp jagged edges.
  • Not ideal for huge tanks

SevenSeaSupply Ohko Dragon Stone Rock

Make way for the versatile Ohko Dragon Stone Rock which can turn your aquarium into a haven for your tiny friends. These stones mimic the river bed and ocean floor, so your fish and plants feel at home in your miniature ecosystem.

These rocks have crannies, nooks and hiding places for nano fish, shrimps, and cichlids. Schooling fish that swim all together in sync can get through these rocks like playing “hide and seek.”

You bring nature back to your pets because Ohko rocks can offer a place for breeding and dwelling. It’s also a safe shield from intense light.

They might look unsightly for you, but that is how nature caused these rock formation. They go into curing and sterilization before trading them, so they are in excellent condition,  but you also need to rewash them to avoid cloudy water.

Capture the eyes of the viewers by adding creative rockwork with these Ohko Dragon Stone Rocks. These lava rocks formed through erosion has natural hollows, crevices, and holes.


  • Aesthetic appeal
  • Lightweight
  • Natural Tan Color
  • Inexpensive
  • Packed with premium rocks in different sizes


  • Dusty-looking
  • Brittle and can break

American Fireglass LAVA-M-10 American Fire Glass Black Lava Rock

Transform your tank into a natural lava rock aquarium through these premium stones from American Fireglass. Add life to your overall setup by bringing back nature to your tank’s occupants.

Adding these rocks can replicate tropical and oceanic habitats that your fish will find sanctuary with. They form these rocks through erosion, that is why they are black.

They vary in sizes, texture, and structure weathered by the acts of nature. These were not for tank decoration, but as aquascaping evolves, they included the exotic lava rock aquarium theme.

These lava rocks are your investment because they capture the eyes of onlookers when they realize they came from molten volcanic magma.

You can use it in several ways possible, for home decors,  table art, fillers on bowls and vases. They have an excellent burning effect, so they’re best for outdoor fire pits and fireplaces indoors.

Black lava rocks are inexpensive without sacrificing quality. They only need low maintenance; they’re long-lasting and have a high magnitude of porosity.

Remember how to prepare rocks for aquarium by washing them. They are not fancy faux rocks that look shiny and clean at once, lava rocks can look untidy, but the good news is you can tidy it up, spend some time.


  • Natural lava rocks
  • Perfect for indoor and outdoor use
  • Durable
  • Cost-effective option
  • Low maintenance
  • Porous


  • Can invite the growth of algae
  • Dusty when not washed

Penn Plax Stone

If you were to choose what’s the best rock for a freshwater aquarium? Natural or human-made, faux yet exquisite or an exotic one from volcanic magma?

Penn Plax Stone can give us all the looks! Its stones exude visual interest. They are granite replicas from solid resin materials.

The large and flat ones are stackable. They are sturdy and durable, safe to use in salt and freshwater tanks.

They made large openings and holes in these rocks to provide your fish in a resting place, a hide-away, breeding areas, and a dwelling place for a more extended period.

You can order additional stones depending on the design you want to display. You can customize your structure.

Some designs will suit your cichlids and some fish colonizing a territory. Build multiple swim-through sanctuaries where your fish can conceal against aggression and stress.

Bring back the ocean life or tropical environment of your fish by adding these natural-looking aquascaping rocks by Penn Plax.


  • Premium granite rocks replicas
  • Aesthetic appeal for both fish and viewers
  • Solid resin is safe for tank use
  • Durable and sturdy
  • Customizable according to fish sizes
  • Multi-purpose
  • Use in tank regardless of water salinity


  • Large fish can get stuck
  • Stones are fragile in its pack
  • Nothing beats the natural lava rock

Final Thoughts

In summary, in buying the best foundation for a freshwater aquarium, there are many things to consider. Do you want the natural one or human-made imitation? Are you for the looks or the benefits?

Research fish tank gravel ideas, decide and plan to avoid choosing random rocks. If you do not know how to cure the rocks first, do not attempt getting rocks from nature or bodies of water.

Rocks from polluted areas are detrimental to the welfare of all the inhabitants in your tank. Do not use metallic rocks. You may settle for fancy faux rocks or glow-in-the-dark stones, but make sure they are pre-sterile upon purchase, then wash them over and over before using.

Regardless of your reasons, the aquscaping rocks that I have reviewed in this article are some popular ones available. Any of these will contribute to making a spectacular aquascape that will catch your viewers in awe and leave you satisfied.

2 comments on “Your Guide on the Best Rocks for Freshwater Aquarium”

  1. Lava rocks give awesome look in an aquarium. You can use lava rocks undoubtedly in yours. But you cannot put it in your aquarium directly, you have to prepare it before placing it. So, follow the steps below:
    You can clean them with fully clear water and make them clean. But we will mention some more useful methods with you. We can wash the rocks for 30 min with clean water, then it will be clean to use in the aquarium.
    You can boil the lava rocks in water for 30 minutes. It will remove all dirt and clean the potential diseases from the rocks. After boiling them, wipe them with a clean towel, then we have to cool them for one hour. Then we can use them in aquariums.
    We can also use bleaching powder. We can use 1:10 portion in water and keep the rocks in the solution for 24 hours. They will be clean and disinfectant. Then we can use them for aquariums.
    You can visit more resources to know more about lava rocks issues. Enjoy your new lava rock decocation, I can guarantee you will love it.

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