Introduction

In rivers and streams, aquatic plants can grow naturally in the sandy and muddy gravel beds. The type of substrates varies according to environmental condition and geographic location. According to some aquarists, the substrate is usually warmer than the surrounding environment. The temperature difference creates convection current which provides water circulation in the substrate. As water circulates through the substrate, it provides a continuous supply of nutrients to the roots.

Substrate system in planted tank refers to the media use at the base of the tank, normally in the form of soil, sand or pebbles. The main functions of a substrate system are:

• Act as a rooting media for aquatic plants
• To provide nutrients for the plants – Aquatic plants absorb nutrient through their roots and leafs, depending on the types of plants and the types of nutrients.
• Media for the growth of beneficial bacteria – All planted tank needs beneficial bacteria to convert harmful substances (Ammonia, Nitrit) into useful substances (Nitrate, Nitrogen) that aquatic plants can use. Substrate is a good place to cultivate these beneficial bacteria.

Not all the substrate system can perform the above 3 functions readily. For a substrate to act as a rooting media, the size of the substrate must be appropriate – in general smaller size substrate can act as a better rooting agent as compare to bigger size substrate. It is a common practice in planted tank that the upper most layer of the substrate consists of the finest (smallest) substrate, follows with the bigger size substrates underneath. While many do this for aesthetical reason, it also has the practical usage – finer substrate on the top layer provides a better rooting media for new grown root to attach itself. 

As for providing nutrients, some commercially available aqua soils do contain certain nutrient that is useful for aquatic plants, however, most of the sands and pebbles do not. Nutrients can be added into the substrate either during the initial tank set up or can be added in subsequently.

• Nutrient Rich Substrate

This layer of substrate provides the aquatic plants continuous supply of nutrients until the available nutrients are depleted. The types are nutrients vary according to individual manufacturers. There is a wide range of such nutrient rich substrate in the market and the following are some examples:

A type of nutrient rich substrate that is of coarser grain size.

A type of nutrient rich substrate that is of finer grain size.

• Gravel or inert substrate

Some substrates are inert – contain limited or no nutrient. This kind of substrate is often used for decorative purpose or at the area in the tank where it will not be planted and the following are some examples:

A type of coarse grey gravel.

A type of fine gravel.

Based on our experience, there is no right or wrong in using nutrients rich substrate or gravel. Every type of substrate has its advantages and disadvantage.  For example, we use nutrients rich substrate for most tanks because apart from acting as a rooting media, it can provide a fertile base for our plants to grow.  You can observe that almost 90% of our tanks in the gallery section uses nutrients rich substrate because of the above mentioned. 

Beneficial bacteria in a planted tank need to be specially cultivated, natural growth of bacteria is either too slow or in effective. “Seeds” of beneficial bacteria can be added into the substrate system during the initial tank set up and replenishing the bacterial at certain interval throughout the tank life. Bacterial that are being added into the substrate during the initial tank set up are normally in dried powder form and it is commercially available, these are the special strain of bacterial cultivated to convert harmful substances in a planted tank into useful or at least harmless substances. Bacteria can also be added in concentrated liquid form during regular tank maintenance. Having an effective and healthy colony of beneficial bacteria is often an importance key to the success of a planted tank (which many has overlooked).

Therefore, a very important thing to do before you start to purchase your substrate is to list down what are your objectives & consideration so that you can make a better decision.

Note: Depending on the aquatic planted selection, it is also possible to have a planted tank without any substrate system, but it will be an extreme case that will not be discussed here.