What plants need

Water

Aquatic plants are in general very sensitive to the water quality. Although some plants, such as the floating fern, are easy to keep, and seem in different to the quality of the water, others require water that is soft and acid or,alternatively, alkaline and hard, and will only flourish in water that is adapted to their specific needs.

Light

Aquarium plants usually need strong lighting, produced by special fluorescent tubes for 12 or 13 hours a day. If the lighting is deficient in either quality orquantity, the plants will turn yellow and eventually die.

Carbon dioxide (CO2), oxygen (O2), and photosynthesis

Like all living beings, plants are continuously respiring. They consume oxygen and expelcarbon dioxide, the reby affecting the oxygenation of the water, both in anatural setting and an aquarium.
By contrast, in reaction to light – the refore only by day - they absorb the carbondioxide from fish respiration and produce oxygen: it is this photosynthes is that enables them to grow. This phenomenon has a beneficial effect on the equilibrium of the aquarium, as it results in the production of more oxygen than the plant consumes in its respiration. There may be slight ariationsin the oxygen levels from day to night, with the minimum levels being reachedin the last third of the night. An aquarist (preferably an insomniac!) can verify this by measuring the pH every hour in a cycle of 24 hours (see diagram on page 14). An increase inthe water's oxygen level pushes up the pH, while the production of CO2 at night acidifies the water and the pH goes down.
This phenomenon, which is only really visible in heavily planted and denselypopulated aquariums, rarely entails any problems for fish.

Fertilizers

When an aquarium is put into operation, the bed and the water contain mineral salts.These gradually run out and the plants are the refore in danger of mineral deficiency. Faced with this situation, an aquarist has three options:

-regularly change part of the water (generally 10% of the volume per week), toobtain "new" water containing salts;

- addliquid fertilizers specially designed for aquatic plants;

- addsolid fertilizers, in the form of sustained

-releasemineral salt capsules placed at the base of the plants.

You can also make a solid fertilizer at home, based on clay. Knead it, form smallballs, then have them soak up liquid fertilizer. Placed at the base of plants, these balls gradually release their nutrients.

Mineral salts

This name covers all the substances needed for the growth of aquarium plants. They are infact the equivalent of the fertilizers that are used in agriculture, or for house plants. Plants' needs vary according to the substance: some are only required in tiny amounts (metals, for example) but they must be constantly available. Mineral salts are absorbed by the roots and leaves in truly aquatic plants, and by the roots in amphibian plants. In the natural environment, some aquatic areas are considered fertile,as the renewal of the water and the equilibrium of the natural cycles provide sufficient amounts of mineral salts for plants to prosper. Those regionslacking these vital elements are characterized by sparse vegetation, or none atall.In an aquarium, which is a self-contained environment,the water and the bed contain mineral salts that will gradually run out, at arate determined by the quantity of the vegetation. You must there fore make plans to reinforce the mineral salt level on a regular basis, as you would for house plants. Some aquarists provide, from thevery beginning, an enriched soil that will gradually release these mineral salts. This is particularly useful when possible to find veritable "aquatic horticulturalists"who obtain astonishing results.

How doyou know if your plants have a growth problem?

A plant lacking any of the elements it needs to live turns yellow or brown and rapidly dies. The leavesget covered with a fine layer of filamentous algae and eventually fall off.However, in some species it is not easy to tell when the growth process is slowingdown. extensive planting is envisaged for the aquarium (in the case of aDutch aquarium, for example ).

The Dutch aquarium

In this type of aquarium fish serve as a foil to theplants, which play the leading role, althoughthe former do also contribute to theequilibrium of the setting, which is not easy tomaintain. The plants and fish can come fromdifferent geographical areas. Theresults can be ravishing, sometimes amountingto a veritable aquatic garden, with theaquarist becoming a horticulturist in orderto maintain it.