There is an essential substrate for each type of aquarium. If you were growing live plants in the tank, choosing the best aquarium substrate is an important decision that will have long-term effects on your plants because many live plant species draw their nutrients from the substrate. Each plant has different requirements, and you should consider the resources of each available substrate material and use what better meet your plant’s needs.
On this post, we will have a look some of the most important things to consider when choosing a substrate for planted tank and some of the commonly used substrate materials. Also, we will share some substrate ideas that can we use for plants to help you get started on the right foot.
Planted Aquarium Substrate
Before we use a substrate for planted tank, there are some things to consider in choosing the right material.
# Should be Fluffy and oxygenated
A good substrate should be not too soft also not too dense, that mean it provides good circulation and root penetration. Some substrate materials will compact rapidly while some others will stay fluffy for a long while.
Unfortunately, every substrate will eventually compact over time and not get oxygenated very well. In anaerobic condition (without oxygen), toxic substances such as hydrogen sulfite may build up. In addition, a solid substrate will prevent nutrients from reaching the plant roots. So, here are a few tips to keep your substrate fluffy and oxygenated for a long time:
- Mix the aquarium substrate on a regular basis or adding Trumpet snails that will burrow through the substrate, will help to release gas before they build to deadly proportions. This will also keep the substrate fluffy oxygenated.
- Use light material such as vermiculite and perlite in your substrate. This will makes it fluffy and oxygenated.
- The grain size is important. It should be selected such that it is neither too fine nor too coarse. Too fine materials will tend to become solid over time. Gravel that is too coarse won’t offer a very good foothold for the plants and excess fish food, and waste can settle into it which eventually lead to water quality problems in the long run. The best grain size is about 2-3 mm.
A deeper substrate (3+ inch) does not get oxygenated very well and may compact faster. When the aquarium substrate is too thick, or becomes compacted and can lead to hydrogen sulgide buildup.
# Inorganic vs organic materials
Organic materials will eventually decay which will eventually bring problems such as hydrogen sulfide formation. Organic materials offer a short-term supply of nutrients which will eventually have to be replenished with solid fertilizer, so you might as well just use inorganic materials and avoid the problems associated with decaying organic matter. In most case, the organic substrate must be replaced after a period of 12 to 18 months.
Many aquarists will use a couple of handfuls per 20 gallon tank as a first layer to give a little boost at the beginning. That quantity should not be a problem in the long run.
# Not too deep, not too shallow
The depth of the substrate for planted tank is really important. The best way to find how deep your substrate aquarium must be is to know what plants you want to grow.
Plants species such as Anubias, Mircosorium, and fern could do without substrate while plants such as Echinodorus and Cryptocoryne will requires plenty of room to grow their root systems.
A sloped substrate (shallow in front and deeper at the back) can be a great way to accommodate all plants. Larger plants with correspondingly larger root systems in the back, smaller plants with correspondingly small root systems in the front.
As a rule of thumb, 2-3 inch at the back should be enough for most large plants. In less depth, deep-rooted plants will become entangled and the aquarium plants will suffer from a lack of nutrients.
Preferably, the planted aquarium substrates should be filled with ample amount of nutrients in forms that can be readily absorbed by the plants. The easiest way the substrate can be fertilized is by using substrate materials that are already rich in nutrients. Otherwise, there are fertilizer tablets which can be purchased and pushed down into the substrate, releasing nutrients over time.
It is important not to overdose nutrients in the substrate. A substrate that is too rich will eventually leak nutrients and trigger algae growth. To prevent the substrate to leak, it is a good idea to use substrate materials that are rich in nutrients such as clay, peat and soil as a bottom layer and to top it off with another material to seal it.
The Captation Exchange Capacity (CEC) is also an important thing to consider when choosing your aquarium substrate. CEC is the ability to adsorb positively charged nutrient ions (so high CEC is good). This means the substrate will hold nutrients and make them available for the plant roots. It doesn’t indicate a number of nutrients the substrate contains.
# Effects on water chemistry
Some aquarium substrate materials will dramatically change the water chemistry. You have to make sure it is not loaded with limestone or calcium that can lead to uncontrolled hardening of the water. You want it to be inert. If in doubt pour some muriatic acid on the substrate material you want to use. If it bubbles, fizzes, smokes or dissolves then avoid it.
The Best Substrate for Planted Aquarium
Here is a short list of aquarium substrate materials that can be used as the substrate for planted tank. Some of them can be used alone while some others should be mixed with other materials.
CEC: High | Inert: Yes | Organic: No
Eco-Complete is one of the best planted aquarium substrates today. This is a well balanced and easy to use. Eco-Complete that doesn’t require too much rinsing, which something most don’t like to do.
It comes with essential nutrients and minerals needed for live plants and will not impact your water parameters. The grain sizes are within range for optimal root growth and the appearance is a deep black sandy gravel. It’s also rounded gravel and poses no threat to bottom feeding fish which may hurt themselves on the sharp-edged substrate. This substrate can be expensive, but it’s worth the money. It can be used on its own, mix with other ingredients or as a top layer.
CEC: High | Inert: Yes | Organic: No
Flourite is a clay based substrate with a reddish color that comes from its high iron content. It is very rich in nutrient. Nutrients in it won’t leak into the water column. In addition, Flourite doesn’t get soft in water. Like Eco-Complete, this substrate can be use on its own, mix with other ingredients or as a top layer.
Unfortunately, Flourite needs to be rinsed extensively before putting in an aquarium. Otherwise, it will cloud up the water. It doesn’t have as many minerals and nutrients as other planted aquariums substrates, but it’s still an excellent choice.
3. ADA Aquasoil
CEC: High | Inert: Yes | Organic: No
ADA Aquasoil the best-planted substrate money can buy. Made up of round grains, the substrate maintains gaps allowing for water circulation to prevent roots from suffocating. Aquasoil also acts as a passive filter, capturing floating particles.
This substrate can be expensive, but it’s worth the money. It can be use on its own, mix with other ingredients or as a top layer.
I never tried Aquasoil so can’t tell much about it. It’s certainly a good choice but I always try to stay away from it because of the price.
4. Fine gravel
CEC: Most have a low CCE
Inert: Should be. May contain calcium carbonate which may raise your pH undesirably.
It can be used alone or mixed with other aquarium substrate materials. When used alone, regular gravel is certainly not the best but it works. Gravel contains no nutrient for the plant’s so more intensive fertilization will be needed.
Another way to use gravel is to mix it with other substrate material or to use it as a top layer to seal the bottom layers, so they won’t leak nutrient into the water.
Inert: Should be. May contain calcium carbonate which can increase pH undesirably.
Can be used alone or mixed with other aquarium substrate material. We need more intensive fertilization if used alone because sand contains no nutrient for the plants.
Many aquarists use sand as a top layer but it makes planting stem plants difficult because it is not heavy enough to hold the plant in place. In addition, sand is not very effective for sealing nutrient into the substrate which may cause problems. Finally, most sand will compact over time.
On the other hand, sand is generally easy to keep it clean as debris remains on top of the sand. Sand is a natural substrate, so any inhabitants of your tank will feel right at home along the bottom of the tank.
6. Potting soil
CEC: High | Inert: No | Organic: Yes
Potting soil available from gardening centers can also be part of a good substrate for planted tank. Soil tend to contain appropriate amounts of humus and can be a valuable source of many nutrients, especially trace nutrients. Many aquarists have been using potting soil mix with sand and vermiculite as a substrate for years and really like it. I have heard of dozens of successes and very few failures. However, you have to be careful with potting soil. You’ll have to make sure to pick one that has had no additives or fertilizers added.
Potting soil will also leak ammonia which will trigger algae growth. A good way to fix this is to cook the soil for a good hour at 350F. This will turn the ammonia into nitrate.
Always top it off with another material. Otherwise, it will mess you water really bad. Let the soil in water six weeks before setting up the aquarium so all the initial chemical reactions will take place and the soil will “bubble up” most of the gasses from these reactions.
CEC: High (82.0 – 150.0) | Inert: Yes | Organic: No
Vermiculite is a micaceous material resulting from an expansion of granules of mica at high temperatures. It should be mixed with other material and should not be used on it’s own. Always top it off with another material. I only found a few recipes that suggest the use of vermiculite. Vermiculite is characterized by its lightweight and high water-holding capacity.
Vermiculite gradually releases nutrients for plant absorption; on average it contains 5-8% available potassium and 9-12% magnesium. It can fix ammonium into a form that is not readily available for plant absorption. This fixed nitrogen is gradually transformed to nitrate by microorganisms, making it available for plant uptake.
CEC: Very low (1.5 – 3.5) | Inert: Yes | Organic: No
A mineral of volcanic derivation that may be used in some substrate mixes. Perlite has a very low Captation exchange capacity, low water-holding capacity (19%), and neutral pH. The closed-cell composition of perlite contributes to its compaction resistance, enhances media drainage, and heightens the aeration of the substrate. Be aware of possible aluminum toxicity in acidic media (pH < 5).
Perlite contains, on average, 47.5% oxygen, 33.8% silicon, 7.2% aluminum, 3.5% potassium, 3.4% sodium, 0.6% iron and calcium, 3.0% bound water and 0.2% magnesium and trace.
Perlite is characterized by approximately 70% total porosity, 60% of which is aeration porosity. Perlite can retain two to four times its dry weight in water, which is much greater than that of sand, yet much less than the water-holding capacity of peat and vermiculite. Never use it on its own and always top it off with another material.