Substrates in the aquarium
Plants use the substrate to grow their roots, but the purpose of growing is to get nutrients or reproduce. Plants have a different root system, which grow better in different types of substrates. In nature aquatic plants evolved to get use to specific conditions, which are nothing like regular pea gravel. To create more suitable environment for your plants you will have to consider different size and shape of aquarium substrates, how deep will be the layer, and how rich in nutrients and minerals it will be.
Size and Shape
If the size of the substrate is not good for the plant it will cause problems. Too big shape will cause that nutrients will be washed from the roots and plants, won’t grow too well. On the other hand to small substrate will be compact so well that it won’t allow enough oxygen to go thru it, and may cause damage to the roots system. Good size of aquarium substrate could be size about 0.04-0.12 in (1-3mm) with round shape. Sharp substrate may damage the roots.
Dirt as a main rooting substrate dirt is used often as a rooting medium, because it holds nutrients very well. It should be compact enough to prevent excess and capped between other substrates.
You can mix 0.08-0.12 in (2-3 mm) substrate with others more rich in nutrients.
Nutrient-rich substrate will provide nutrients continuously for a long time. Those kind of nutrients are usually compacted very well and are kind of soil looking. It is good to close it in lower layers so it won’t get water muddy. It may use as a main rooting substrate. Below are some different types of the substrate you may want to know.
Top level substrate most visible usually used as a thin layer, is more like a decorations medium than rooting medium.
Pea gravel is the most popular form of aquarium gravel. It is round, usually small and has different color. Smaller grades can be used as a main substrate cause it holds nutrients(debris) well between its particles. Aquatic plants won’t get much benefits from the pea gravel.
Quartz gravel often knew as a lime free gravel might be used as a main rooting medium and as well as a to layer, because of it’s black color. Its grades are usually between 0.04-0.12 in (1-3 mm) so it is good for keeping aquatic plants. It provides better support for plants than pea gravel.
Sand using a sand may cause a problems because its small grade may be to compact, not allowing enough oxygen to get into the roots. It is used sometimes as a bottom layer together with the heating cable. It is one of the methods which was popular in the past, because it pushes natural water movements from the substrate and nutrients from the water to the substrate. It needs to be moved gently and regularly from time to time, to prevent anaerobic conditions and toxins build up. With heating cable it is good to use no more than 1.6 in (4 cm) of sand, then water movement will deliver enough oxygen all the way to the bottom of the sand.
Laterite/day substrates known as a clay-based substrates, are mainly available as a addiction to the substrate. You won’t need it much because it is very rich in the nutrients, and having a lot of it also may cause problems like algae. It has reddish color, because it is reach in iron and releases it for a long time. It is the best to use it as a layer by the bottom third of the substrate or mixed in the middle, where the fain roots absorbs their nutrients.
Nutrient-rich substrates those substrate are design specifically for planted tanks. Some of them are based on the laterite or contain mix of the good organic nutrients and minerals, which will be released continuously even thru 3-4 years. Substrates like this is good to use in small quantities, as a thin layer or mixed with the other substrates.
Soil-based substrate if you are beginner, it is better to avoid soil in the aquarium, because it is very unpredictable. If you will get more experience with aquatic plants, you may try to use soil based substrates as long term planting medium. Soil contain big amounts of carbon and iron which will benefit aquatic plants, as it will be slowly released to the water and absorbed by the roots.
Aerobic and anaerobic substrate conditions
A substrate rich in organic material (waste matter and nutrient-rich substrates) will naturally contain large numbers of bacteria that break down these organics into usable nutrients. The majority of these bacteria quickly use up oxygen, with the result that the substrate becomes anaerobic. In anaerobic conditions, different types of bacteria form, which do not need to use large quantities of oxygen or can create their own oxygen. These anaerobic bacteria can release toxic gases, most notably hydrogen sulphide, which can cause plant roots to rot, damage fish health, and encourage algae to flourish.
However, anaerobic conditions also allow nutrients to become more readily available to plants by preventing the binding of nutrients with oxygen molecules. As the bacteria use up the nitrates, nitrogen is released, which is also an important plant nutrient.
A mixture of aerobic and anaerobic substrate zones can provide the benefits of both conditions. As long as the substrate is not too fine and compact and/or substrate heating is employed, the combination of a slow-moving current and the release of oxygen by plant roots should prevent the majority of the substrate from becoming anaerobic. Anaerobic patches will then appear in denser areas of substrate without plant roots. Because these patches are small, they will not produce large amounts of toxic gases yet still allow nutrients to be produced and available to the plants. So a low-oxygen substrate is often best, where anaerobic conditions are allowed to develop in some places but not in others.
I was using nutrient-rich substrates like eco-complete, caribsea floramax original and black, and I noticed that 4 inches of the substrate is an optimal level (minimum) for the keeping big bunch of plants in your planted tank. Some plants after few months will produce huge roots, which probably would be even bigger if I would have more than 4 inches of substrate.So, it could probabely grow bigger. I also noticed that if you will put some pebbles on the top, plants will grow faster because more debris and nutrients will accomodate in the substrate, but it is also harder to clean and cause a risk that the substrate will be too compact and not enough oxygen would get to the roots. Also not vaccuming a substrate too often helps keep plants fed better. I’ve never been using any root tabs and my plants have never been struggled or showin any defiancies. Never do deep substrate vaccuming, only the top layer.