Whether you’ve made the leap to a planted aquarium, or are thinking of making the switch, chances are you’ve had to spend some time thinking about substrate.
What you use to line the bottom of your tank is often the basis for healthy, strong plants, and a vibrant, diverse ecosystem.
Many aquatic plants are very similar to those in your garden. They take up nutrients like magnesium, potassium, nitrogen, and iron from the substrate in the bottom of the tank.
These nutrients enable the plants to photosynthesize and grow just like their Earth-dwelling counterparts.
There are many different kinds of substrate available, and not all types are suitable for all plants. Some in fact, aren’t suitable at all. So it can be a daunting task to try and figure out which is best for your needs.
This article will cover everything you need to know about choosing the right substrate for planted aquariums, and help you decide which is right for your particular tank.
At a Glance: Our 4 Recommendations for Best Substrate For a Planted Tank
- Carib Sea Eco Complete Planted Black Aquarium Substrate
- Seachem Flourite
- ADA Aqua Soil Amazonia
- Fluval Plant and Shrimp Stratum
Note: The links above take you to more information, current prices and customer reviews on Amazon.
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What is Substrate?
Generally speaking, a substrate is any material that lines the bottom of your aquarium.
What you choose to use will affect the chemistry of the water, the filtration process, and for planted tanks, the health of your ecosystem.
Substrates also play a part in your tank’s aesthetic appeal. It’s one chance for you to style your tank in an individual way, with a wide array of different sizes, colors and textures to choose from.
What are the Benefits of Using Substrate in a Planted Tank?
First of all, it’s essential for plants to grow. The most important benefit of the substrate in a planted tank is it’s impossible for many (most) plants to grow without it.
Yes, there are floating plants or those that can anchor to driftwood, but most aquatic plants need to develop a good root stock and to draw essential nutrients through these roots to feed the rest of the plant.
To develop a good root system, a stable, firm, deep and suitable substrate is required, in exactly the same way as is needed for your garden plants and trees.
Secondly, it helps fish feel they’re in a natural environment. Any fish for which you mimic their natural habitat in your home aquarium will be happier, less stressed, will behave more naturally, quite likely live longer and will just in so many ways benefit from your efforts.
Fish do not naturally live in glass or acrylic boxes. So by lining your tank bottom with a substrate close to what they would see in the wild, will encourage natural behaviors and ‘make them feel at home’ as it were.
Finally, it looks good. Yes, we’ve said this before, many times, but in our opinion, a more natural looking aquarium just looks better in our eyes. A slice of nature recreated in your home.
Different Types Of Substrates
There are a few different common types of substrate, not all are great for planted aquariums. Let’s take a quick look at the most types available, with some pros and cons.
The most commonly used substrate, it’s cheap, plentiful, comes in many sizes and colors offering a good chance for you to personalize your tank, and is common in many fishes natural habitats.
It’s far from the best substrate for plants, but is suitable for many, especially if fine gravel. However, there are dangers with fine gravel as some fish may ingest it, or get it stuck in their mouths. Also, make sure you buy aquarium gravel which is rounded with no sharp edges, not gravel meant for other stuff.
You might also be interested in:
- Our top choices for best aquarium gravel vacuum
After gravel, sand is the second most substrate seen in home aquariums. Again, it’s cheap, readily available, and comes in many colors. (Note: We have an extensive guide to the best aquarium sands here.
Many riverbeds and seabeds are lined with sand, so it is a natural environment for many fish we might keep at home and presents a good environment for those who like to dig or bury themselves.
Sand does have some pitfalls, such as clouding the water if kicked up, potentially clogging filters, and worse of all can form pockets of poisonous gases if fish waste or uneaten food gets buried and decomposes in an anaerobic environment. However, it is better for plant root systems than is gravel, though still not the best.
Marbles are exactly as they sound, little disc-shaped (not completely spherical) pieces of glass. They are more an aquarium decoration that a decent aquarium decoration and many plants will struggle to root properly in marbles and will not be able to take up any nutrients from them.
This is a substrate used most in saltwater or reef / marine tanks, to most closely mimic the natural environment of tropical sea fish from coral regions.
Coral sand can best be described as a very large particle gritty sand. It is good for rooting plants, and particularly for coral-dwelling fish, but it does have the issue of raising the pH levels of your tank as it dissolves over time.
Soil or Clay
Soil or clay-like substrates are a fantastic option for planted tanks, being densely packed and stable, offering the best medium in which plants can spread out and create healthy, strong, nutrient sucking root packs.
Soils and clays can hold and deliver the highest concentration of nutrients for plants compared to any other option.
You do have to consider which soil or clay type you use, as some can change the water chemistry (those labeled as ‘active substrate) while some do not affect the chemistry of the water (those labeled as ‘inert.’)
What is the Best Substrate for Planted Aquariums?
In most cases, it would be an aquarium soil substrate.
They are stable and dense, allowing plants to develop very strong root systems. They also contain more essential nutrients than any other type which is important for growth, and are closest to what most plants would live in out in nature, and give the best chance for them to thrive.
They can look a bit dull compared to other substrates, not offering any chance to personalize your tank with different colors, but they can be mixed with another substrate, or a 2nd layer of another can be placed on top if you so wish and really have a desire to put your stamp on how the bottom of your aquarium looks.
How Much Substrate Should You Use For A Planted Aquarium?
Generally speaking, 2 to 3 inches of substrate is recommended for a planted tank.
If you’re using a soil-like substrate, then 2 inches will suffice, more will not hurt, but anything over 2 inches is just overkill, takes up too much tank space and reduces the volume of water you can have. It’s just not necessary.
If using something coarser however, such as coral sand or gravel, aim for 3 inches just to give some extra room for plant roots to spread out and anchor themselves well in what isn’t as dense and stable as soil.
What to Consider When Choosing Substrate for a Planted Tank
The substrate you choose to line the bottom of your tank will affect the overall health of your planted aquarium, so it’s important to do your research ahead of time and get this right.
Get it wrong, and depending on your plant choice, they may have next to no chance of survival.
Below are some things you need to consider to help you choose substrates that will contribute to the health and beauty of your planted aquarium.
What do the Plants You Are Planning Actually Need?
This assumes of course that you’ve got an idea of what plants you’d like to grow in your aquarium?
Some plants like a tightly packed substrate, while others prefer it looser. Some grow well in acidic substrate, while others require a more alkaline medium.
The more you find out about your plants’ preferences, the better you’ll be able to plan for the right substrate.
There is also a wide range of substrates that are appropriate for most (but not all) planted tanks. If you’re just starting out with a planted tank, you may want to check out these ‘all-rounders’ and get hardy plants for beginners, rather than going expert level and for varieties that require very specific and specialist care.
Substrate Particle Size
From tiny particles of sand to large pieces of gravel, substrate comes in all kinds of shapes and sizes, but does size matter? It certainly does!
Smaller substrate particles may clog together, leading to anaerobic conditions within your tank, where no oxygenated water can reach your plant roots, leading to unsightly and toxic hydrogen sulfide production.
Tiny particles may also be sucked into your cleaning siphon, clog the filter, and generally just cause trouble.
Larger particles, on the other hand, will allow more food to accumulate on the bottom of the tank, falling into the gaps between the gravel of marbles, causing a potentially toxic environment for fish if not properly cleaned.
How deep your substrate layer needs to be, largely depends upon the type of plants you are growing.
Shallow-rooted plants will do fine in as little as 2 cm, while deep-rooted varieties will need 6 cm or more for proper growth.
However, there’s nothing to say substrate has to be the same depth throughout a tank. You can vary the depth in different areas of your aquarium based on the plants in different areas, gently sloping the depth from shallow to deep, going one side to the other, or from back-to-front.
Just remember that the deeper your substrate, the more you have to worry about anaerobic pockets creating harmful toxins for your fish. 7 or 8 cm should be your absolute maximum depth, even for deep-rooted plants.
Nutrients in Substrate
There are some aquarium plants that must get many of the nutrients they need from the substrate you provide.
Plants need both macro- and micronutrients to survive and thrive:
- Macronutrients are nitrogen, phosphorus, and potassium, which must be consistently available for proper growth.
- Micronutrients Such as copper, zinc, and manganese are trace elements that your plants need in minute quantities.
Your plants will get most of their nitrogen from fish waste, and much of their potassium from fish food. Other macro and micronutrients though are either necessarily supplied by your choice of commercially available substrates or added as a fertilizer to the water.
Some of these nutrients will be immediately available to your plants from the substrate, while others are stored and released slowly throughout the lifecycle of your aquarium ecosystem.
If your plants need it, the substrate you use as a planting medium should be rich in nutrients to provide optimal growing conditions.
As most nutrient-rich substrates tend to be quite dull in color, a colorful gravel or another aesthetically pleasing material can be used as a top layer so you can still customize your tank.
Best Substrate for Planted Tanks – Our Top 4 Recommendations
There are many products on the market, and truth be told most of them are good enough. But of the many available, here are the 4 we deem to be some of the very best and are happy to recommend.
Carib Sea Eco-Complete is made of incredibly nutrient-rich volcanic soil containing both macro and micronutrients for proper growth. It is a one-stop-shop, easy to use, nutritionally complete soil suitable for any freshwater planted aquariums – though note, it is not for saltwater or marine.
First of all, Carib Sea describe this themselves as ‘bi-modal,’ and go on to explain that it naturally separates into two layers in your tank. Finer stuff works it way down and creates a dense bottom layer for the best rooting for plants, while larger, coarser grains settle on top forming a second layer that aids the transfer of oxygen and nutrients to the roots.
It contains Iron, magnesium, potassium, zinc, sulfur and a whole plethora of other nutrients, too many to list here, but everything your plants need to thrive, and no extra ingredients, second substrate layer, fertilizer or anything else needs to be added.
This substrate also contains live micro-organisms which help establish the nitrogen cycle and balanced water parameters, plus there’s no need to rinse the product before use, just place it directly into your tank.
Another benefit is it doesn’t contain any artificial chemicals, colorings, or any other additives.
It’s also a naturally dark black color, which helps to make your fishes color pop against it and in my opinion, looks great and quite natural in the bottom of any aquarium.
This is an excellent choice of substrate and is our number one recommendation for freshwater planted tanks.
- Naturally attractive without the use of chemical paints or dyes.
- Naturally rich in nutrients.
- No need to rinse before adding to your aquarium.
- Nothing else needs to be added, it’s an all-in-one complete solution for planted tanks.
- There is an initial smell before you add it to your aquarium.
- It’s for fresh water tanks only.
- It may raise the pH of your tank slightly for a few weeks (easily remedied, but you should be aware of this!)
This is a nutrient-rich, porous clay gravel that never needs replacing and feeds nutrients throughout the lifetime of your aquarium.
It isn’t chemically treated, has no nasties in it to affect your water parameters and is completely inert, however it does need a good rinsing before you add it to your tank or it will cloud the water quite heavily.
Fluorite can be used as a stand-alone substrate, or it can be mixed with gravel or sand if desired.
It is especially rich in iron, for lush, vibrant plant growth.
- Beautiful red color.
- Rich in iron, which is perfect for plants on the red spectrum.
- Never needs replacing.
- Can be mixed with gravel or other inert substrate.
- Extremely dusty. Must be rinsed very well before adding it to your aquarium.
ADA Aquasoil Amazonia
This specially formulated substrate was created to mimic the soil in the rainforest, made from (they claim) a rare source of Japanese plant-based decomposed leaf mulch to result in dark black soil.
This most closely imitates what you would find on many inland riverbeds, is completely natural and organic, and so is ideal for planted tanks.
This is an ‘active’ substrate, meaning it will change the water parameters. In this case, ti will soften the water, lowering the pH. Therefore, it’s a great option for aquariums with plants and fish that require a lower pH but doesn’t suit all tank inhabitants. Make sure you match this up carefully.
The consistency of ADA Aquasoil is fine granules, which keep their shape for a good long time, enabling oxygen into root systems, while providing a good solid medium for plants to spread their roots and form a solid base.
You can add a second layer of another substrate on top if you desire and want to change the look of your tank.
- Nutrient-rich for optimal growth.
- Keeps water nice and clear.
- Doesn’t need rinsing.
- Dark in color, which will enhance the coloration of your fish.
- Naturally lowers the pH, so not ideal for plants that thrive in an alkaline environment.
Fluval Plant and Shrimp
This mineral-rich, volcanic substrate is perfect for all kinds of plants and is specially designed to support shrimp growth.
This mineral-rich product promotes a neutral to mildly acidic pH level to stimulate the growth of aquatic plants and also being perfect for a range of freshwater fish species.
Macro and micronutrients are readily available, and its porous structure is beneficial to nitrifying bacteria that help maintain balanced water parameters.
Don’t be put off by the ‘plant and shrimp’ labeling if you have no shrimp, it’s great for planted tanks, with or without the crustaceans! Marketed as ‘non-compacting,’ it allows plants to spread their roots and form a good solid base while allowing oxygen and nutrients into the root systems.
The size of the particles also allows the baby shrimp fry to dig themselves and hide, giving them a greater chance of survival in a community tank with inhabitants who might like to make them lunch.
- Will not cloud or discolor water.
- Provides a refuge for newborn shrimp.
- Light and non-compacting.
- Lowers pH slightly.
- Very lightweight, making it difficult for bare-rooted plants.
- Must rinse before using.
Planted Tank Substrate FAQ
A few commonly asked questions, to which we will add to as time goes by:
Do Aquatic Plants Need Soil?
Not all aquatic plants need soil. Some plants float, and others attach to rocks and logs. While some rooted plants will anchor just fine in plain sand or gravel, many need some kind of soil to grab onto and to draw nutrients from. Using soil will encourage lush growth of your rooting aquatic plants.
Is Sand Substrate Cleaner Than Gravel?
Because sand grains are very small, there are no spaces for waste material to accumulate like it will in gravel. In that sense, sand is cleaner. However, this also means good bacteria, which help the nitrate cycle, won’t grow in sand. Also, sand can be harder to vacuum since it is so fine.
If you have a good filter that draws from the bottom of the tank, you may find sand to be a cleaner choice, especially if you have burrowing fish to stir it up.
Can I Use Garden Soil in an Aquarium?
You can make your own aquarium soil using soil from your garden, or bought from a garden center. Be sure to use only soil marked as “chemical-free” or “organic,” or chosen from part of your garden where pesticides and fertilizer are not used. Also, do not use peat, as it will turn the aquarium water acidic.
Soil must be sifted and conditioned before use. To learn more about prepping garden soil for aquarium use, we recommend reading this article.
Can I Use Play Sand in an Aquarium?
Yes. Inexpensive play sand is an appealing alternative to expensive aquarium sand in both planted and unplanted tanks. If you plan to use it, use only new sand and be prepared to rinse it thoroughly and repeatedly.
Play sand has a lot of fine particulates and will make aquarium water silty if it isn’t rinsed first.
How Deep Should the Substrate Be in a Planted Aquarium?
The depth of your substrate will partially depend on the kinds of plants you want to use. Some plants either float or attach to wood and rocks and require no substrate at all.
Plants with long roots, like Echinodurus and Cryptocoryne, will need a minimum 2-3 inches (5-7 cm) of substrate. Allowing for the maximum will allow you the most options in the future for plant choice.
How to Set up Substrate for a Planted Aquarium?
After choosing your substrate material, the first step is to rinse it clean, even if it’s new. By rinsing out the fine particulate and any pests (like snails) or contaminants, you’ll find it much easier to keep your tank clean.
Put down several inches of substrate to accommodate all kinds of rooting plants. You may wish to add a layer of sand or gravel on top of the soil, but this is optional.
Add water carefully to avoid disturbing the substrate and dirtying the water. A good tip is to put a plate on top of the substrate and pour the water over the plate. For a thorough look at setting up a planted tank, try this step-by-step guide.
Planting and maintaining a complete and natural aquatic ecosystem has never been easier.
Nutrient-rich, organic substrates are a simple way to create beautiful, planted habitats that are suitable for all kinds of plants and in turn fish species.
Because there are so many options available, you can choose a substrate that will meet the needs of any tank.
Most substrates can be mixed and matched, giving you all sorts of options for a healthy, beautiful planted aquarium that still allows room for personalization and a sense of your own style to it.
Happy fish keeping!
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