When setting up a new aquarium, choosing the right substrate is one of the most important decisions you will make. After all, the gravel you go with will likely stay in the tank for its entire lifetime. It doesn’t go bad, after all, and it takes even more effort to remove it once it’s in place.
This guide will help you prioritize what’s most important to you when shopping for gravel. And I’ve also included a listing of my personal favorite gravel blends to consider!
Aquarium Gravel and Fish
Nearly all fish tanks use gravel, pebbles, sand, or some other substrate to line the bottom. In most cases, the exact kind of substrate you use isn’t all that relevant. There are really good arguments for using any of the above to cover your tank bottom! We will explore many of the most important buying decisions below.
But what about aquarium gravel and fish? Is there a single best aquarium gravel for your particular fish? The answer is: it depends.
It depends mostly on the kind of aquarium fish that you have. Bettas, Tetras, Livebearers, and other midwater to surface-dwelling fish that only come infrequently to the bottom of the tank are not very picky. You can keep them in an aquarium with sand, fine pebbles, big chunks of gravel…It really does not matter.
Cichlids are midwater to bottom-dwelling aquarium fish that do a fair amount of digging. Gravel with sharp edges or grains that are far too large can damage their lips when they build holes for spawning preparation.
Corydoras, Kuhli and Clown Loaches, Spiny Eels, and other bottom dwellers that like to burrow are even more strongly affected by rough gravel grains. They should only be kept in tanks with fine pebbles with smooth edges. Sand bottomed tanks are even better for these fish.
What Should I Look For in an Aquarium Gravel?
Why Aquarium Gravel Color Matters
The color of your fish tank stones affects not only the beauty of your tank but also your fish! When kept on pale substrates and bright lighting many colorful fish tend to show washed-out colors. This is due to their instinctive desire to blend in with their environment. Colors that are too bright make them much easier targets.
In environments that are less well lit – or balanced by a dark substrate – fish colors tend to darken in response. A natural brown, tan, or black bottom can make them look significantly more vibrant.
Still, if you really enjoy a light tan or white substrate color, using plants and other sources of cover will encourage your aquarium fish to remain vibrant.
Unnatural colors like pink, blue, or green are also options and have the same benefits and drawbacks for fish color, depending on the hue. Substrates for Glofish is often one of these shades or even dark black aquarium gravel mixed with a few grains of other colors. When lit by a black light, the effect is ethereal, more like a rave than a traditional aquarium but extremely beautiful!
Aquarium Gravel for Planted Tanks
Choosing aquarium gravel for planted tanks is a little more complicated. Because the substrate is the “habitat” of many freshwater plants. Whether you plant in gravel or sand, the substrate is where many nutrients collect. A good substrate allows for proper water flow and oxygen exchange to occur as well, which many plant roots require to grow properly.
Something else to think about is that different plants may have differing gravel needs. For example, many carpet plants prefer fine gravel grains. Many even prefer sand because the individual plants and their roots are so small. They can’t root properly when the gravel grains are too large. Some plants are entirely flexible while others prefer medium to large grains over fine gravel grains.
Inert versus Active Aquarium Gravel
Something else to think about is how your planted tank substrate holds nutrients. There are two categories of aquarium gravel for plants: inert substrates and active ones.
An inert substrate is one that does not contain nutrients. Standard aquarium gravel, which is made of rock and silica (SiO2), has no nutrients that plants can access. It is effectively sterile out of the bag.
Even many gravel designed for planted aquariums is inert. Being inert isn’t necessarily a bad thing, though. You can easily add fertilizer tablets underneath the substrate to make up for this if your plants are root feeders. And since nearly all plants also take in nutrients through their leaves dosing with liquid fertilizers can make an inert substrate a non-issue.
Lastly, many planted tank inert substrates have the ability to absorb nutrients from the water column. They have a high cation exchange capacity (CEC), allowing them to bind elements and chemicals to their inner pores. The roots of plants will eventually find and release these agents to be used by the plant.
Active substrates, on the other hand, already have nutrients contained inside them. Many even have organic matter like peat, bits of wood, and other material that helps cultivate beneficial bacteria. These bacteria consume the organics, breaking them down into essential nutrients that plants can then uptake. Active aquarium gravel may be stone, or more commonly, baked clay or soil.
How Much Gravel Do I Need for my Aquarium?
Buying the right amount of aquarium fish gravel matters a lot when setting up a new tank. After all, you don’t want to be run out and end up with too little gravel or have too much leftover. The dimensions of your tank and the thickness of your substrate are the most important aspects to consider.
For a gravel tank, 1.5 to 2 inches of depth is typical for most aquarists. Less than that can also work, though an inch or less of gravel gives plants a lot less to work with. Any digging fish will quickly expose the bare glass. And since the gravel tends to hide fish poop, leftover food, and other debris until your next water change, a deep substrate keeps the tank looking clean for much longer.
This helpful Aquarium Gravel Calculator will give you a better idea of the exact amount you need for your aquarium!
The Best Freshwater Aquarium Gravel
1. River Rock Stones by Voulosimi
I’ve always been a fan of the natural habitat look for aquariums and these polished river rock stones by Voulosimi are some of the best! These are landscaping, plant, and aquarium pebbles that are variable in size and color, from black slate to pale quartz stone.
At ½ of an inch to an inch in size, these grains are ideal for fish of any size, though they offer no digging potential for burrowers like cichlids and catfish unless they are larger fish. Many have found that the stones do have a slight coating that needs to be washed away when first purchased.
2. GloFish Aquarium Gravel
Glofish are one of the hottest new additions to the aquarium hobby! These genetically engineered fish don’t use injected dyes to glow; they produce fluorescent pigments organically thanks to their coral and jellyfish DNA.
GloFish Aquarium Gravel is one of the best gravel choices for these fish because of how dark and high in contrast it is. The dark black with fluorescent highlights is the classic choice but neon pink, blue, green, and other colors are also available.
They are meant to be displayed under a black light, which causes both the bright grains and fish to take on an ethereal glow. Unlike natural gravel grains, the colors for GloFish Aquarium Gravel are painted on, which gives them a deep, dark appearance and highly consistent look!
3. CaribSea Eco-Complete for Planted Aquariums
CaribSea Eco-Complete is one of the most popular freshwater fish tank gravel choices for folks looking to start their own planted tank for the first time. It looks great, with small, round pea-sized grains that also have smaller grains mixed in for a not quite uniform but unmessy look.
The gravel is also packed with live beneficial bacteria, helping to jump-start new aquariums by getting the nitrogen cycle started quickly. Floraspore mycorrhizal symbiotic fungi are also packed, which partner up with plants to help their roots get established faster. It’s one of the few, if not only, premixed live substrates for freshwater aquariums!
Something to keep in mind when considering Eco-Complete is that the wording on the packaging is a little misleading at times. For instance, they give nutritional info on the back of the label, breaking down the ratios of iron, magnesium, calcium, and other nutrients that plants need.
The problem is that these are all bound up in the rock matrix of the gravel; they are as nutritious for plants as they are for you in this form. It’s not lying, but it is misleading. However, it does have a good cation exchange capacity, allowing it to bind fertilizers and other nutrients for your plants to later use!
4. Seachem Flourite
Seachem Flourite is another inert substrate designed for planted tanks but works just as well as fish gravel! While Eco-Complete is made of volcanic soil, Fluorite is actually baked clay. Clay has an even higher cation exchange capacity for floating elements but it is also fairly inert. It does have some bioavailable iron though, which is helpful for plants.
Seachem Flourite is mostly inert and has very little effect on the pH of your aquarium as well. Having used it myself, it is very, very dusty, though. It takes multiple rinses to get it clean enough to add to your tank. And even then, the water will be cloudy for a few hours or days until it all gets filtered out or settles.
But I think it’s worth the hassle. Flourite has an excellent balance in terms of color consistency, grain size, shape, and biological activity. It’s the best substrate for folks that want a natural look but also like a little bit of polish! It also comes in several colors, including ruddy brown, red, onyx grey, and black!
5. Polished River Rock Pebbles by BLQH
If you really enjoy the natural river pebble look these stones from BLQH are well worth a look! They have a glossier coating than the ones offered by Voulosimi yet require no rinsing beforehand. These stones are also a little more uniform in size and shape.
Sometimes we need to be careful with rock-based substrates because some rocks are soluble in water. Limestone, shale, and other sedimentary and metamorphic rocks can often raise or lower the pH. But the coating of these pebbles makes them entirely inert since water can’t reach the rock to dissolve minerals within! The colors are also quite subdued, making them ideal for natural aquascapes and betta aquariums!
6. Fluval Plant and Shrimp Stratum
Fluval Plant and Shrimp Stratum is one of the most popular soil-based aquarium gravels for very good reason. It’s pH neutral, unlike many soil substrates. In fact, it actively buffers the pH towards neutrality, which is ideal for the vast majority of fish, plants, and especially dwarf shrimp.
The grain size is small enough for carpeting plants and other light rooters yet large enough for bigger plants to securely root. And the spaces in between the grains are large enough to allow for good oxygen and nutrient flow to the roots.
Fluval Stratum is also a porous substrate, allowing fine root hairs to penetrate it and for bacteria to colonize it. It’s by far the most natural option if you’re looking to create a space for both fish and plants to thrive!
7. Natural Slate Stone by Small World Slate
Slate stone is a favorite for aquascapers because it has the look of shale; flat slabs of polished black rock. However slate won’t drop the pH like shale does since the rock has been chemically altered over millions of years (metamorphic rock).
Small World Slate uses small fragments of the stone offered in volume most suitable for betta bowls and aquariums up to 5 gallons in size. The pieces are far too large for plants to root in unless they are epiphytes like Java Fern or Anubias. Each fragment is around ½ inch to an inch in size. Given the sharper edges, I would avoid adding these to tanks where the bottom-dwelling fish have soft whiskers or scaleless flanks.
8. Mixed Polished Gemstones by Goldshine
For folks looking for something with even more polish Goldshine’s 7-12mm gravel grains are ideal! These stones are natural gemstones, including marble, chalcedony, lazurite, and other stones with fine swirls and subtle colors.
All of these rocks are mostly inert in water and many have an intriguing rectangular shape to them that stands apart from traditional round grains. The only real downside is that you would need to buy quite a few pounds to fill up even a small freshwater fish aquarium. Which might get pretty costly. But then, you’re buying gemstones, so that should be expected!
9. Granite Mini Pea Gravel by Maynooth Natural Granite
Granite Mini Pea Gravel is another natural-looking substrate that uses rock instead of soil. These truly are pebbles in terms of size, with grains that are not too large or too small. Granite (granitic gneiss) is an excellent choice for aquarium pebbles because it is fully inert and won’t cause shifts in pH. Therefore there’s no need for chemical coatings to keep it away from the water.
This mini pea gravel is a little on the rough side so don’t add it to tanks with fish that have soft whiskers or skin like Corydoras. And since it comes in 5 lb bags you can quickly and affordably fill an aquarium with this stone gravel! If you are a geology lover then you will appreciate the information that Maynooth collects on both their gravel and the area.
The grains have patterns of milky quartz, microcline feldspar, and muscovite mica, among other identifiable minerals. This gneiss is sourced from the Canadian Shield region, which is some of the oldest rock on the planet.
10. Pisces Midnight Pearl Aquarium Gravel
Pisces Midnight Pearl Aquarium Gravel is a blend sourced from the beaches of New Zealand. These stones have been polished by ocean waves over millennia and are a mostly dark blend of stones that are ideal for natural aquascapes.
Pisces triple washes its gravel so you don’t have to. It can go straight from the bag into the tank. At 2-4mm in size, the grains are small and smooth enough not to cause harm to fish or plants. Yet they are also large enough for you to fully appreciate the diverse blend of rocks and minerals contained within each bag.
The Pisces company actually has a sizable collection of affordable, beautiful natural aquarium gravel options, including a pale tan Gold Pearl option and a very unique Gunsmoke blend of subtle grey stone! Each of their listings also shows how the stone looks both wet and dry, in case you wish to use some for planting and some as your fish tank gravel.
In Conclusion
Choosing an aquarium substrate that makes your tropical fish and live plants look good is an important decision. After all, you will be looking at it for a long time and it is hard to change out. The “best” aquarium gravel is really a personal choice. But hopefully, some of the options I’ve laid out here will give you some ideas.
Aquarium Gravel Frequently Asked Questions
Some kind of substrate is always a good idea unless you intend on setting up a bare bottom tropical fish aquarium. Gravel is not the only choice but is the most practical and versatile option. Most freshwater fish either enjoy it as an aquarium substrate or don’t mind swimming over it.
The exact amount of aquarium substrate depends on how large your tank is and how deep of a substrate you want. As a very rough rule of thumb, you can try buying 1 lb per gallon of water. This works fairly well for standard and “long” style tanks.
When choosing planted aquarium gravel you want something that either has a high cation exchange capacity (CEC) or is enriched with nutrients. You can use standard (inert) gravel as well so long as you are dosing with the right fertilizers to compensate for the lack of nutrients.
