A Guide to the Best Rocks for Freshwater Aquarium

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As a fishkeeper, I have a deep affinity for rocks in the tank. It completely changes the looks and aesthetics of the whole system. Apart from the visual benefits, Rocks for Freshwater Aquarium actually improve the ecosystem being home to hundreds of beneficial bacteria and algae.

You should already know that rocks, especially corals, are an essential part of a saltwater aquarium. But can you use rocks in a freshwater aquarium?

Of course, you can use rocks in a freshwater aquarium, but you need to be very careful about the type of stone. You can't just add any rock in your freshwater aquarium.

So, what are the best rocks for freshwater aquarium?

There are a lot of options available to you. So, let's dig deeper into the matter and find out more about the rocks in the aquarium.

New fishkeepers need to understand one thing first – aquarium rocks are not just another decorative element. 

Apart from giving your tank the soothing natural look, it creates hiding places for the smaller fish and is a breeding ground for the beneficial microorganisms.

So, first of all, I will discuss the core benefits of having rocks in your aquarium.

Additional Food Source

Some fish eat the algae grown on the rocks and woods. So, you can add a natural food source for your fish. It goes without saying natural food sources are always better than artificial ones.

Denitrification

Every single fishkeeper has to worry about the presence of ammonia, nitrites, and nitrates in the tank. There is simply no escape from the nitrification process.

The good news is that a lot of beneficial bacteria build colonies on the rocks. These bacteria actively take part in the denitrification process.

So, the addition of rocks can help you improve the water quality of the tank.

Creating a Natural Vibe

The secret to seeing your fish thrive is to create an environment similar to their natural habitat. I have hardly seen fish living happily in a barebone glass tank.

The rocks and the plants invite different microorganisms that create a pseudo-natural ecosystem, even in a small tank.

So, having rocks in the aquarium will help you create better living conditions for your fish.

Creating Hiding Places

Fish often get spooked due to many reasons. Sometimes due to seeing new people, sometimes seeing other fish in the tank, sometimes due to some unknown reason.

The thing is fish tend to cower in some narrow corner when they are afraid.

Having rocks mean that they have such shelter in the tank. So, you are creating that essential protective layer for your fish.

The Safe Rocks List for Your Aquarium

Carib Sea Base Rock

If you are looking for a solid base rock to give your aquarium a soul, Carib Sea South Seas Base Rock should serve you perfectly.

It's a dry dead rock that you should use in a marine aquatic system. If you are keeping African Cichlids, you can use it as they have a higher tolerance for alkalinity.

As the rock is quite soft, you can process it and shape it up as you prefer – chisel it, drill it, break it. You have all the options for customization.

These rocks are the results of hundreds and thousands of years of erosion and pitting. So, you will be getting perfectly natural rocks that you don’t have to cure to use.

The Rock Profile – Carib Sea South Seas Base Rock

Rock Type

Sedimentary rock

Main Component

Limestone (calcium carbonate)

Weight

40 pounds

Aquarium Type

All marine tanks, and high pH freshwater tank

Reasons to Choose

 - 50% void space percentage combining micro and macro holes

 - Naturally formed rocks made of eons of erosion and pitting

 - Soft and can be cut with simple hand tools

Worldwide Atlantic Coral Rock

We all know, coral makes the best-looking rock for any saltwater aquarium. What could be better than having your coral stones collected from the Atlantic?

I think the best feature of this live coral is the presence of beneficial bacteria colonies. The rocks create a superb biological system in your tank. You will have a great filtration system as a bonus.

As these are natural live corals, you can just add them to previous coral sets, and they will bind together naturally!

The Rock Profile – Worldwide Imports AWW0855 Atlantic Coral Rock

Rock Type

Sedimentary rock

Main Component

Calcium carbonate

Weight

40 pounds

Aquarium Type

All marine tanks

Reasons to Choose

 - Natural coral rock collected from the Atlantic Ocean

 - Live rock will need less maintenance

 - Comes with natural beneficial bacteria to boost biological system

Nature's Ocean Base Rocks

The Nature’s Ocean 12-inch Coral Base has all the good features of the previous one and more. This is also another live coral. 

Nature’s Ocean has harvested these corals for coral farmers and live rock culturing. Moreover, these corals have been soaked in the deep wells so that leaching doesn't occur.

This rock can be a great addition to your marine aquarium.

The Rock Profile – Nature's Ocean 12-Inch Coral Base Rocks for Aquarium

Rock Type

Sedimentary rock

Main Component

Calcium carbonate

Weight

40 pounds

Aquarium Type

All marine tanks

Reasons to Choose

 - Serves as a biological filtration system due to hundreds of holes

 - Deep-well water treatment prevents leeching incidents

 - Natural live coral reefs

ARC Reef Dry Rock

ARC is offering a different type of reef stackers that are harvested and mined from the earth. Typically, dry reef rocks come from reefs and intertidal zones, which might contain dead organisms.

ARC guarantees that you will not have to cure these dry rocks as they don’t contain any phosphate or nitrate.

Despite being mined from the earth, they have high porosity. The best part about these rocks is that you can place them in your tank instantly without any delay.

The Rock Profile – ARC Reef All New! Reef Stacker Dry Rock

Rock Type

Sedimentary

Main Component

Calcium carbonate

Weight

10 pounds

Aquarium Type

Any marine tank

Reasons to Choose

 - Fully treated, doesn’t need any curing before use

 - Very porous, full of crevices and holes

 - Doesn’t contain silica or other harmful elements

Carib Sea base rock bag

What if you don’t large chunks of rocks but smaller pieces as you have a rather small aquarium?

Carib Sea ACS00372 comes in a 3-case package that contains 10 pounds of rock in total. You can create a nice base with small and beautiful chunks of rock.

It creates a perfect home for the coralline algae. So, your white rock will turn pink very soon with the algae.

You will not have to go through the time-consuming curing processes as these rocks are fully cured.

The Rock Profile – Carib Sea ACS00372 3 case South Sea Base Rock Bag for Aquarium

Rock Type

Sedimentary (Dry live) rock

Main Component

Limestone (calcium carbonate)

Weight

10 pounds

Aquarium Type

All marine tanks, and high pH freshwater tank

Reasons to Choose

 - Fully cleaned, doesn’t contain any bacteria

 - High amount of micro and macro porosities

 - Doesn’t need any curing

Carib sea life rock

Now, I will be talking about a very rare rock collection. CaribSea can offer you real petrified corals! If you have some idea about the marine fishkeeping, you should know how magnificent these petrified corals look in a tank.

Caribsea collects these corals and cleans it gently without any bleach or other chemical agents.

Although the coral is petrified, you will get real aragonitic base rock that comes with spored bacteria. You don’t need to cure it but clean it gently and place it in your tank.

The Rock Profile – Caribsea Life Rock

Rock Type

Sedimentary rock (petrified coral)

Main Component

Calcium carbonate

Weight

40 pounds

Aquarium Type

All marine tanks, and high pH freshwater tank

Reasons to Choose

 - Beautiful coloration

 - 50% void space percentage with lots of holes and crevices

 - Unbleached and not chemically treated

Deep Blue Small Texas Holey Rock

Deep Blue Professional is offering a synthetic rock that you can use both in the freshwater and saltwater tanks. Moreover, these are very cheap compared to the other ones that I just mentioned in this list.

Why so?

Because this is the only fake rock in my list today. Being artificial, these rocks tend to be very light too – weighs only about one pound!

But I have to give credit to the designers as it looks very natural live. Also, there are a lot of holes and pores on the surface. The inside of the rock is hollow.

You can even hide different devices beneath it.

The Rock Profile – Deep Blue Professional ADB80403 Small Texas Holey Rock Synthetic Coral for Aquarium

Rock Type

Synthetic coral

Main Component

Synthetic elements

Weight

1.3 pounds

Aquarium Type

Freshwater and marine water

Reasons to Choose

 - Plenty of hollow space inside for hiding

 - Budget-friendly

 - Doesn’t affect the water chemistry

Buying Guide to Choose Best Rocks for Freshwater Aquarium

Not every rock is so helpful towards the fish. Some of them could pose a lethal threat to the fish also.

So, obviously, you need to think strategically before choosing any rock for your freshwater aquarium.

What to Look for While Choosing Rocks for Freshwater Aquarium?

 - Go for Vibrant Colors

Colors play a massive role in defining characteristics of the rocks. That being said, I would suggest you pick the red, pink or purple rocks.

Why?

Such vibrant colors suggest the presence of healthy coralline algae living on them. These algae enhance the aquatic environment of the tank.

The fish also feel cozy living with these kinds of colored rocks.

 - Crevices and Holes

Avoiding fully sold rocks might not be a smart decision as to the crevices, and the holes serve as the hiding or resting places for the smaller fish.

Moreover, these coarse corners will eventually become bacteria colonies.

No, not for the bad ones, but the good ones!

 - It Shouldn’t be Slimy or Smelling Funny!

Two types of rocks should be on your avoiding list – the black slimy ones and the ones that smell funny.

These signs mean that that rocks have dead entities on them, which could b extremely dangerous for the fish in the tank.  

In fact, you might be bringing in the havoc, creating diseases with these rocks.

Moreover, when choosing the rocks, avoid the stones that come with unknown living organisms for the same reasons.

 - pH Balance

This is a big factor in choosing a rock for your aquarium. You need to get the rocks that don't mess with the water chemistry.

For example, a lot of people use limestones in the tank. Limestones are primarily made of calcium carbonate with some traces of calcites and aragonites.

Calcium will heavily impact the pH level of the water. Saturated calcium carbonate has a pH level of 9.4, which very alkaline. That’s why I would call limestones to be one of the unsafe Rocks for Freshwater Aquarium

Aquarium pH level should be somewhere between 6.5 to 7.5 for most of the aquarium plants and fish.

So, make sure that your rock will not drastically change the water chemistry or hamper the pH balance.   

 - Price and Size

Aquarium rocks can cost about $5 to more than $100. There are a number of facts that pile on the costing of a rock.

Mostly, size plays the major, deciding the price of an aquarium rock. No matter what rock suits your needs, always buy from a trusted source.

Also, the size of the rock should match the size of your aquarium. Something too big or too small can hamper the natural flow of life in the tank.

Types of Aquarium Rock

I wouldn’t go too deep into the categories – you and I will both drown by the overwhelming number of types of rocks.

Based on the aquarium type, the basic classification is as follows –

  •  - Freshwater tank rocks
  •  - Saltwater tank rocks

    Both the freshwater and saltwater rocks are a good place for the beneficial bacteria colonies. But due to the nature of water chemistry, there is a significant change in the rocks' composition.

    For example, aragonite sand is a very common element that forms a lot of saltwater live rocks. But aragonite sand isn’t a very good option to add in freshwater tanks.

    However, this is not a very useful classification of Rocks for Freshwater Aquarium. So primarily, the aquarium rocks can be of three types –

    • - Igneous rocks
    • - Sedimentary rocks
    • - Metamorphic rocks

    - The Igneous Rocks

    This type of rocks comes directly from the core f the earth. That's why some call this type to be the "real rocks."

    The molten rocks coming from the core of the earth cool down over time and forms the igneous type of rocks. I personally find this type to be exotic and fascinating.

    Typically, the igneous rocks tend to be –

    •  - Basalt
    •  - Dolerite
    • - Gabbro

     - The Sedimentary Rocks

    These are the most common type of rock found in various parts of the world. Initially, these rocks start from sedimentary accumulation from flowing water. After layers and layers of accumulation, the final form starts to appear.

    You will probably find these rocks near fountains, rivers, seashores, and creeks.

    Some example of the sedimentary type of rocks are –

  •  - Limestone
  •  - Sandstone
  •  - Conglomerate
  •  - Shale
  •  - Marl
  • - Breccia

    The Metamorphic Rocks

    The word, metamorph means change. As you can imagine, these rocks go through some form of natural change over time and turn into such kind of rocks.

    Mostly, heat and pressure play the most critical impact on such changes. 

    Are you looking for some examples?

    Here they are –

  • - Marble
  • - Quartzite
  •  - Slate
  • - Gneiss
  • - Dolomite
  •  - Hornfels
  •  - Schist
  • FAQ: Time to Answer Your Questions on Aquarium Rocks

    Can I Use My Own Outdoor Gravel or Rocks in Aquariums?

    People often like to collect rare and beautiful looking rocks when they travel or camp in forests. So, can you use any kind of natural outdoor rock in your aquarium?

    No, I would suggest not to!

    The main reason is that you can’t possibly know the actual type of rock that you have collected (unless you are a geologist!). There is a chance of your rocks to have toxic properties.

    Moreover, some rocks can change the pH level that can have some serious impact on water chemistry in your aquarium. 

    If you collect the gravel from the earth, it is almost certain to have bacterial colonies on the surface. You can' be sure of the nature of these bacteria, either. It can be beneficial or completely lethal for your fish. 

    So, don’t take any chance! 

    How to Prepare Rocks for Aquarium?

    Most of the gravels that you buy from a brand tend to have dust on them. So, you should clean them off before placing them into your fish tank.

    First of all, you need to get a strainer and a bucket. Noe place all the gravel or the rock on the strainer. Now gently pour water on them.

    You will notice that the drained water is unclear or cloudy from the dust particles of the rocks. After pouring water continuously for some time, you will notice the water turning clearer every time.

    Once the drained water turns completely clear, your rocks are ready for the aquarium.

    Personally, I have seen a gallon of water is just perfect for treating a pound of rocks. Still, you should pour water until it becomes clear.

    Where to Find Rocks for Aquarium?

    As I have said, buying rocks is a much better choice compared to finding your own rocks from nature. 

    Your local pet shop or dedicated fishkeeping shop should contain all kinds of rocks for both the freshwater and saltwater tanks.

    You can also get the rocks from online shops.

    Don’t worry, you can rely on them as long as you are getting your rocks from a reliable brand.   

    I have always got my rocks from Amazon and have never faced any unhappy situation.

    More: Best Sand for Reef Tank

    How to Clean Rocks for Aquarium Use?

    No matter how clean your aquarium is, you might need to clean your aquarium rocks. Otherwise, the rocks will be polluting the water badly.

    Mostly, the rocks turn slimy and dark due to algae habitation.

    As there are fake aquarium rocks and live natural rocks, you need to follow different cleaning methods.

    You will mostly work on the cleaning procedure on the fake decorative rocks. Cleaning live stones frequently might not be a good idea.

    If you have the fake ones in your tank, you can use a good algae scrubber every month when you change the water of your tank. You should scrub thoroughly to get rid of all the algae.

    But don’t use tap water to wash the rock. Instead, you should use the dirty water from the tank to rinse it off.

    You should never use a scrubber on live rock. The good thing is that you don't need to clean these rocks that often. If you have a biological filtration system, the live rocks shouldn’t have algae sitting it.

    If you have to use a brush to clean it off, make sure to use one with softer bristles. After the soft touches from the brush, place it in saltwater for a day or two.   

    Conclusion

    So, what are the best Rocks for Freshwater Aquarium? Carib Sea South Seas Base Rock stands on the front of the line taking the number one spot.

    Worldwide Imports AWW0855 Atlantic Coral Rock bags the second position being the best rock for marine tanks. 

    Obviously, the third place goes to Nature's Ocean 12-Inch Coral Base Rocks for Aquarium which is also the best budget rock for freshwater tank.

    What do you think of the picks?

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