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Home » Planted Aquarium Substrate, Planted tank basis

Substrate materials for the planted aquarium

Submitted by on April 14, 2009 – 10:24 pm19 Comments


There is an appropriate substrate for each type of aquarium. If growing plants is what you want, choosing the right substrate is an important decision that will have long term affects on your plants because many plant species draw their nutrients from the substrate. Each plant has different requirements and you should considers the properties of each available substrate material and use what better meet your plant’s needs.

Rather than going through every single substrate combination, we will have a look some of the most important things to consider when choosing a substrate and some of the commonly used substrate materials. In another post, we will have a look at some substrate ideas to help you get started on the right foot.

Things to consider

Should be Fluffy and oxygenated
A good substrate should be rather « fluffy » (not too dense), meaning that 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 prevents nutrients from reaching the plant roots. Here are a few tips to keep your substrate fluffy and oxygenated for a long time:

-Gently mix the aquarium substrate on a regular basis or adding Trumpet snails that will burrow through the substrate, will help releasing 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.
ß 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, organic substrate must be replace after a period of 12 to 18 months.

Many aquarist (including myself) 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 is really important. The best way to find how deep your substrate 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 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 of with another material to seal it.

The Captation Exchange Capacity (CEC) is also an important thing to consider when choosing your 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 the amount of nutrients the substrate contains.

Effects on water chemistry
Some 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. Some people will say that vinegar will work for this acid test. Not true (vinegar is too weak).

Substrate Materials

Here is a short list of substrate materials that can be use as substrate. 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 substrate that doesn’t require too much rinsing, which something most don’t like to do.
It comes with essential nutrients and minerals required for live plants and will not impact your water parameters. The grain sizes are within range for optimal root growth and the appearance is of a deep black sandy gravel. It’s also rounded gravel, and poses no threat to bottom feeding fish which may hurt themselves on sharp edged substrate.
This substrate can be expensive but it’s worth the money. It can be use on it’s own, mix with other ingredients or as a top layer.

aquarium substrateFlourite
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 it’s own, mix with other ingredients or as a top layer.
Unfortunately, Flourite needs to be rinsed extensively before putting in the aquarium, otherwise, it will cloud up the water. It doesn’t have as much minerals and nutrients as other planted aquariums substrates but it’s still a great choice. I have been using Flourite for many years and I love it.

aquarium substrateADA Aquasoil
CEC : High
Inert : Yes
Organic : No

Supposedly 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 it’s 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.

aquarium substrateFine gravel
CEC : Most have a low CCE
Inert : Should be. May contain calcium carbonate which may raise your pH undesirably.
Organic : No

It can be used alone or mixed with other substrate materials. When used alone, regular gravel is certainly not the best but it works. Gravel contains no nutrient for the plants 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.

aquarium substrate Sand
CEC : Low
Inert : Should be. May contain calcium carbonate which may raise your pH undesirably.
Organic : No

Can be used alone or mixed with other substrate material. Sand contains no nutrient for the plants so more intensive fertilization will be needed if used alone.
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.

Some common recommendations are for play sand, sandblasting sand or pool filtration sand.
Play sand works well and is cheap but the particles are really small and can get sucked into the filtration system and completely destroy pumps in hours. So if you use play sand as your top layer, make sure to keep your pumps away from the substrate.
Sandblasting sand can be purchased in different grades that would allow for a large enough grain to ensure it would not be sucked into a filter. The main problem with sandblasting sand is cost (50 pounds can be around $100)
According to many aquarists, the best solution is to use pool filter sand. The benefit of pool filter sand is that the grain is smooth and round. Even if it gets into your filtration system, it is not nearly as destructive as other type of sand. The best part of pool filter sand is the appearance; it looks very natural and the fish seem to love it.

aquarium substrateSpecial Kitty
CEC : Low (22.0 – 63.0)
Inert : Some are inert, others will drastically alter your water chemistry.
Organic : No

Kitty litter is more an additive than a substrate. It is a form of clay that contains iron and trace elements. It also act as a sponge to store nutrients. It will gradually softens and become a mud-like substance so it is best to mix it with another ingredient such as gravel or sand and to use it at the bottom of your substrate. The exact amount of clay used in a substrate is not critical. One part of clay per ten of sand or other material will do fine but it could also be used in higher ratios or as the only ingredient of your bottom layer

If disturbed, it will cloud your tank dramatically so make sure top it off with a tick layer of sand or gravel.

Kitty litter is primarily beneficial for deep-rooted plants and heavy feeders, such as echinodorus and cryptocoryne species. It should last for years and can be supplemented with regular doses of liquid chelated iron and mineral trace elements.

aquarium substrateLaterite
CEC : Low (22.0 – 63.0)
Inert : Yes
Organic : No

Latrite is about the same as Kitty litter.

clay aquarium substratePink Clay from Argile TZ
CCE : Low (22.0 – 63.0)
Inert : Yes
Organic : No

Here is another good clay you could use. I find that I get better results with pink clay than with laterite but it’s much more expensive. Pink clay is sold as a beauty product and could probably be found in any good beauty shop. Otherwise, look for Argile TZ on the Internet. You can use it the same way as Laterite and Kitty litter.

clay aquarium substratePeat
CEC : High (100.0 – 180.0)
Inert : No
Organic : Yes. Contains at least 90% organic matter.

Peat is a type of soil comprised of partially decomposed plant material. It is typically found in swamps where the acidic conditions prevent complete decomposition.
Many aquarist use it to mimic the water from ecosystems such as the Amazon river. It will soften the water and will give your water a yellowish color after some time. Soft, acidic water is fine for many aquarium fish, but fish like livebearers and many kinds of cichlid do not like such conditions. Make sure your fish will do well with that kind of water before to use peat.
You can use peat from a garden center, but you do need to be very careful about picking the right kind: make sure to pick one that has had no additives or fertilizers added.

Unfortunately, peat is an organic material that will eventually decay and lead to various problems.

clay aquarium substratePotting soil
CEC : High
Inert : No
Organic : Yes.

Potting soil available from gardening centers can also be part of a good substrate. Soil tend to contain appropriate amounts of humus and can be a valuable source of many nutrients, especially trace nutrients. I 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 (including my own), 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 of with another material. Otherwise, it will mess you water really bad.
Let the soil in water six weeks prior to setting up the aquarium so all the initial chemical reactions will take place and the soil will “bubble up” most of the gases from these reactions.

Using soil submerged can be very challenging and there are many ways to do it wrong. If you think about using soil in your tank, you should definitely get a copy of Diana Walstad’s book, Ecology of the Planted Aquarium. Most people who use soil are following her methods.

And finally, soil contains organic materials that will eventually decay. You will have to replace it after a little while like peat. It is better not to use too much potting soil.

vermiculite aquarium substrateVermiculite
CEC : High (82.0 – 150.0)
Inert : Yes
Organic : No

Vermiculite is a micaceous material resulting from 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 of with another material. I only found a few recipes that suggest the use of vermiculite. However, I really like using it.
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.

perlite aquarium substratePerlite
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, 3.0% bound water, 0.6% iron and calcium, 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 of with another material.


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  5. How to measure co2 in a planted tank


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