What’s The Best Substrate For A planted aquarium?

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Aquarium substrate is an essential part of any planted tank. It gives your plants somewhere to root and provides essential nutrition. But it’s more complicated than simply buying any old substrate and expecting to grow great plants. This may work sometimes but if it doesn’t you’ll be stuck wondering why. 

There are some important things you need to understand about aquatic plants to ensure success. In this article, you will find reviews on some of the best substrates for planted aquariums.  More importantly,  you will find information on finding the best substrate for you.

Substrates reviewed in this article include:

• Carib Sea Eco Complete Planted Black Aquarium Substrate
• Seachem Flourite Red Clay Substrate
• Fluval Plant and Shrimp Stratum
• ADA Aqua Soil Amazonia
• Spectrastone Shallow Creek Premium Aquarium Gravel

What type of aquatic plants do you want?

Not all plants have the same nutritional requirements. Not all plants uptake those nutrients in the same way. Fortunately for us, there are two general categories. 

Those that feed on nutrients in the water column and those that feed on nutrients in the substrate.  While both types can get a little nutrition from the other source it is important to know the difference. There are also plants that fall in between these two categories and are equally suited to feeding on the water column as well as on the substrate. 

If you can’t find a clear answer as to whether your plants are root or water column feeders don’t fret. Just make sure to have nutrients in both the substrate and water column and you’ll do fine. 

Water Column Feeders

Water column feeders get the majority of their nutritional requirements directly from the water. Much of this nutrition comes from fish waste. Most water column feeders are either stem plants or floating plants. 

Due to the way these plants take up nutrients they do not need a rich substrate. While the plants can soak up a little nutrition from the substrate most of it will be a waste. These types of plants really only use substrate as a place to anchor their roots.

Water feeders give you the option to use basic affordable substrates such as gravel or sand. These substrates don’t contain or hold any nutrients but a water column feeder will do fine in them.

Root Feeders

On the other side of the spectrum are the root feeders. These plants take up nutrients the way most of us are familiar with; through the roots. Since they do most of their feeding through their roots they need a substrate rich in nutrients. 

These rich substrates are normally clay or soil-based and have added amendments. These work great for root feeders but they are not essential. Many people have been successful using root tabs in gravel for instance. These root tabs may also be used to recharge a depleted substrate. 

Keep in mind that these richer substrates have organic material that will essentially rot or break down in your aquarium. This will effect your water hardness and pH.

What should you use if you want to grow both types?

What if you want to grow water column feeders and root feeders in the same tank? 

You could use a complete substrate for the whole tank. You may spend a bit more than you need to but all of your plants would thrive. 

You could also mix a complete and an inert substrate. This could be done by mixing them together evenly. Or, you could spot treat and just use the rich substrate where you plan to put your root feeders.

Another more affordable alternative would be to use an inert substrate and amend it with root tabs. 

Hard Water vs Softwater

Do you have hard or soft water? What’s its ph? These water parameters are important because they may affect what substrate or amendments you should use. 

Hard water is water that has a pH of 8.5 or higher. It also has a lot of minerals such as calcium or magnesium. Soft Water on the other hand will have a pH of 6.5 or lower and few minerals present. 

Why is this important? Because the type of substrate you choose may negatively affect your pH. Certain nutrients are locked up and not available to your plants at extreme pH levels.  This can cause a nutrient deficiency in your plants. Not to mention this may kill any fish you have.

Fortunately, many substrates will state on the bag whether or not they alter pH. An active substrate will likely affect pH while an inert substrate will not. For instance, if you already have low pH water don’t add in a substrate that will lower pH further.

So please, get yourself a water test kit and test your water before adding substrate. Test kits are affordable and simple to use. If you need to adjust your pH there are buffer solutions to adjust it up or down. 

What Are the Types of Aquarium Substrate?

Aquarium substrates come in a variety of colors, textures, and intended uses. The most common substrates used in aquariums are complete, clay, gravel, sand, and soil-based substrates.

Complete Substrates

Complete substrates are produced artificially.  They are designed to provide all the necessary nutrients and minerals to your plants. A complete substrate will also likely be biologically complete. This helps to establish the nitrogen cycle in new tanks. 

Minerals commonly found in complete substrates include iron, calcium, magnesium, potassium, and micronutrients. These components make a complete substrate an excellent for sustaining plant life. 

Some complete substrates are also manufactured to inhibit aquatic algae growth. This added benefit can make maintenance of your tank easier (source 5).

Be aware, however. These are active substrates and can affect your water hardness and ph.

Clay Substrates

Clay substrate provides great support for roots and has an excellent cation exchange capacity. This means that it is great at storing and releasing nutrients. Clay is often mixed with other substrates to provide adequate nutrients. 

Common types of clay such as Flourite contain trace amounts of iron and other micronutrients. These are essential for maintaining a healthy planted aquarium. 

Sand Substrates

Sand is a thoroughly cleaned, natural and generally fine substrate. It is a fantastic choice for delicate fish species that like to burrow. 

Sand is an inert substrate. This means that it contains no nutrients and will not affect water pH. So this a decent substrate for water column feeding plants as long as you have nutrients in your water. 

You can also mix sand with other substrates, such as clay, to provide nutrients for root feeding plants.

The type of sand does make a difference. 

The cheap play sand you get at any store isn’t well suited to a planted aquarium. It is too fine and will eventually get packed down. This will make it difficult for your plants to spread their roots through the substrate. To avoid this make sure you get an aquarium specific sand.

Gravel Substrates

Gravel is a common substrate choice for freshwater aquariums. Gravel comes in a multitude of colors and sizes. Coloring can be achieved through a natural process or can be the result of a dying process. 

When looking for gravel as a substrate, it’s important to note the dye. If a dye is composed of acrylic paint, it can be detrimental to your aquarium water chemistry. Ensure the dye is covered by a natural polymer seal.

Gravel can be very coarse and pea-sized, or it can be very fine (source 5). It is composed of any hard, lime-free mineral such as quartz. 

While it is useful and can add aesthetic value, gravel should not be sharp. Sharp gravel can hurt fish who are bottom dwellers or fish that burrow (source 1).

Soil-Based Substrates

Soil-based substrates are soft in texture and versatile. Soil substrates are often composed of peat, which is decomposed plant matter. 

This substrate has a high cation exchange capacity. This is great for storing and releasing nutrients but also has a water softening effect.

If you have a burrowing fish, soil is a soft and safe place for them to create a home. An unfortunate aspect of soil-based substrates is the tendency to cloud the water. This can turn your water a yellow or brown color. 

There are ways to mitigate this which includes sifting, rinsing and drying. For these reasons, soil-based substrates are best left to the more experienced.