Circulation In Plants

Nutrient flow in nature

The substrate acts as a "nutrient sink," trapping nutrients where plant roots can easily obtain them. The nutrients are moved by gentle convection currents.

Heat from the sun warms the substrate.

Water circulation carries nutrients down into the substrate.

The substrate is slightly warmer than the water above it.

Water rises by convection as it is warmed by the substrate.

Water Circulation Plant

Plant roots absorb nutrients from the substrate.

Water circulation carries nutrients down into the substrate.

The substrate is slightly warmer than the water above it.

Plant roots absorb nutrients from the substrate.

Water rises by convection as it is warmed by the substrate.

when keeping aquatic plants can often be attributed to the lack of a good, useful substrate. Clean, Inert gravel creates a fairly biologically Inactive substrate. Because the water flows easily through such a medium, it removes nutrients, cools the plant roots, and creates an oxygen-rich area, all of which are undesirable and hinder the development of aquatic plant roots.

So which substrates are best? This is not an easy question to answer. Some plants do not need any specialized substrates, while a few need no substrate at all! However, for the most part, a mixture of substrates will create an environment suitable for all the plants in the aquarium. The points to consider are: the size and shape of the particles, the depth of the substrate layer, and its mineral and organic content.

Size and shape

If the particle size of the substrate is wrong, it may cause problems for aquatic plants. A substrate made up of particles that are too large will allow water to pass through easily, removing nutrients. Furthermore, debris will collect in the gaps between the particles, which may muddy the water. Large-grade substrates also cause problems for the growth of long roots and should be used only as a thin top layer.

If the substrate is too fine it may compact, halting the movement of oxygen and nutrients, and causing damage to the root structure.

A suitable aquarium substrate should have a particle size of about 0.04-0.12 in (1-3 mm) and be rounded in shape; sharp substrate particles can damage roots. The only exception is sand, which can be used as a thin bottom layer to support heating cables (see page 44).

Substrate depth

Substrate depth does vary a little, depending on which species of plant you are keeping. Plants that produce long roots, such as Echinodorus species and some cryptocorynes, will need a substrate deep enough for the roots to penetrate. If the substrate is too shallow, the roots of these plants will become dense and tangled. In this situation, the plant cannot obtain nutrients and the roots will become starved of oxygen.

Generally speaking, foreground plants do not produce long roots, so it is possible to slope the substrate upward toward the back of the aquarium. This also makes the aquarium appear deeper than it is. A good substrate depth is 2.4-4 in (6-10 cm).

Mineral content

Plants require minerals in small amounts, but it is difficult to provide these through the substrate, although some nutrient-rich substrates do contain the essential minerals that aquatic plants require. In general, the quantities of minerals required by plants are usually readily available in tap water. However, if the source water for your aquarium is relatively soft it may be lacking in these minerals, in which case you can use liquid fertilizers.

More importantly, a substrate should not contain harmful minerals, most notably, compounds with a high calcium content. Limestone and coral-based substrates, often available for marine aquariums, are high in calcium and should never be used in a freshwater planted aquarium. Substrates such as these will increase the alkalinity and pH of the water, making it harder for plants to obtain nutrients and C02.

Organic content

The organic content of a substrate includes organic nutrients, as well as waste matter from the aquarium (mainly

Below: Not all plants need a deep substrate. This Java fern is happy above or below water, but prefers to root on rock or wood. Although unusual, this preference gives the plant an advantage over other species that could not survive in locations such as this.

Aquarium Plant Anchors

from fish). A substrate without any organic matter is simply an "anchor" for the plants and of little other use. You can add organic matter by using a nutrient-rich substrate, which can either be mixed with the main substrate or arranged as a layer between two substrates. Soil and peat have a very high organic content, so use them with care to avoid overloading the aquarium with organic matter.

Choosing substrates

Several different substrates are available for the aquarium, and making the right choices can be a little tricky. It is possible to have a reasonably good planting substrate using just one medium,

Aquarium Plants With Long Roots
Above: This Echinodorus has two distinct root areas: the thicker upper portion is used for nutrient storage, while the thinner lower roots with their numerous fine "secondary" roots are used for nutrient collection.

Right: Sand makes an interesting and attractive substrate for an aquarium display, but it will require regular maintenance to prevent compaction and stagnation.

Aquarium Plant Substrate

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    Do aquarium plants need water circulation?
    7 years ago

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