Water And Bog Plants by Rene Jez

 

The aesthetic value of an aquarium depends on harmony between a few basic components that are essential for ultimate success; these are:-

 

  1.  Harmony between the aquarium and its surroundings in the home

  2.  Internal aquascaping

  3.  Plant selection

  4.  Fish selection

 

In the present article, I would like to discuss the plants as they are probably the most difficult aspect to tackle. A knowledge of how to grow water plants and their basic requirements are essential if frequent failures are to be avoided.

 

Water plants are not as difficult as ordinary indoor plants but maintenance of the proper environment for them does involve certain rules. Of course they do not need watering but a lot of observation and some preventive care are necessary, because signs of growing or dying back are always delayed.

 

Once an environmental balance is struck, all is easy, but the most critical and important factor to settle is adequate light intensity. Probably some 90% of tanks with plant problems are illuminated below the minimum light requirements, with poor plant growth resulting. The lighting regime should be maintained at 12-16 hours daily.

 

The other critical factor is the balance of soluble nutrients and trace elements in the water. Excessive concentrations of nitrate can inhibit the growth of plants significantly, as can large fluctuations in composition of the water.

 

Plants respond to any change in their environment, such as day-night period or differences in light intensity, which can influence the water chemistry. The amounts of dissolved oxygen (O₂), carbon dioxide (CO₂) and calcium carbonate (CaCO₃) are not steady. During the daylight hours, the O₂ concentration rises and the C O₂ is lowered by the plants' life cycle. This causes a rise in pH value but at night the process is reversed.

 

The plant function influencing these changes is photosynthesis, i.e., the utilisation of light energy and nutrients by the chlorophyll cells to produce plant growth. In water low in free, dissolved CO₂, plants are able to utilise carbonates, such as Ca(HCO₃)₂ as alternative sources of carbon and oxygen. However, this process generates insoluble CaCO₃, together with small quantities of Ca(OH)₂ and this is particularly the case in hard waters, such as those from natural springs in limestone or dolomite catchments (as occur in continental Europe). In severe cases, the rise in pH and the whole chemical process can lead to the incrustation of plants with a white insoluble layer similar to that often found on aquarium covers, where aeration bubbles burst and dry out.

 

During the night, both plants and fish breathe oxygen and exhale C0₂, which dissolves in the water, forming a weak acid and lowering the pH. The acid reacts with CaCO₃ and Ca(OH)2 and converts them into Ca(HCO₃)₂. This process is essentially the same as that of shell grit buffering, in controlling the problem of low pH.

 

The other major influence on water chemistry is the feeding intensity of the tank inhabitants and the accumulation of waste products. Buildup of nitrogen compounds can be rapid, some of them being extremely toxic. Fortunately, the breakdown of wastes is possible, through the involvement of microbes, fungi, algae and higher plants. Thus the base for a proper functioning of any ecosystem is a biological balance between producers and consumers.

 

 

Nearly all aquatic plants are able to grow emerse (above the water), if the environment is suitable. Under high humidifies, plants grow in the emerse form more rapidly and multiply readily. Some (Typha, ferns, Spathophyllum, Echinoderus, and a number of Cryptocoryne species) grow in rather dry air, but all need very moist ground or frequent availability of water. Many typically 'bog' plants are offered by the aquarium trade as under-water plants, but the problem here is that most of them live under emerse conditions and do not tolerate long-term submersion.

 

All kinds of plants growing on our planet form the basis of all life, because of their ability to utilise inorganic matter and to photosynthesise. Other living organisms are consumers and depend on plants for food, oxygen, shelter and many other needs. Both groups are interdependent in continuing the chain of life.

 

In the case of life in a body of water, each environmental unit, regardless of size (sea, farm pond, aquarium), has to attain a balanced harmony or it will cease to live. Any sudden shock or failure of essentials will threaten or even kill the unit and, unfortunately, man is often the root cause of such disasters, through his poisoning or upsetting the ecological integrity.

 

In any balanced under-water ecosystem we find:

 

  1.  Inorganic components (water, nitrogen, carbon, etc.)

  2.  Organic components (proteins, sugars, fats, humic matter, etc.)

  3.  Climatic influences

  4.  Producers (autotrophs), mostly as green plants, rooted or floating (Spermatophyta), algae or phytoplankton (Thallophyta) in lighted areas and fungi (including moulds, yeasts and bacteria). With fungi, the boundary between producers and micro-consumers disappears, as moulds are strictly heterotrophic: they depend upon organic matter for their energy and can decompose a variety of organic substances to obtain their needs.

  5.  Microconsumers, releasing inorganic matter as nutrients, after utilising protoplasm. These are called heterotrophs but the distinction between them and the autotrophs is beyond the scope of this article.

  6.  Macroconsumers (fagotrophs), mostly living organisms that consume other organisms or disintegrate matter.

 

Plants growing in water, water-logged areas or within the reach of fluctuating water levels, are classified as aquatic. Mostly, they are green, autotropic organisms, generally attached but occasionally free-floating. They do not commonly depend on seed production but are mostly perennial and propogate by means of runners, tubers, buds or stem fragments. Upon decay, they release organic matter into the water.

 

Unlike land plants, aquatic plants are able through photosynthesis, to build their tissue directly from dissolved C0₂ and other inorganic components and trace elements. The water is actually a 'hydroponic' solution, prepared by nature. In many cases, where the plants are totally submersed, the nutrients, etc. are absorbed directly through the leaves, rather than the roots and the latter function merely as anchorages. The 'waste' is free oxygen but during darkness, this is resorbed to a limited extent, with the production of some C0₂.

 

Aquatic plants with stronger root systems would depend upon them for growth under emersed conditions and many species that are generally considered to be under-water growers (Myrioph,yllum, Ambularia, etc.) can develop a low but sturdy emersed growth.

 

With plants with strong roots systems, that undergo regular cycles of submerse and emerse growth, the situation is more complicated. In the emerse stage, the roots are collectors of nutrients and the above-water structures function much as they do in land plants.

 

Plants with floating leaves have air-filled cavities to provide the bouyancy but these are not present in the submerged parts.

 

The most important macro-elements for plant growth are carbon, hydrogen, oxygen, nitrogen and potassium; the essential trace elements include iron, boron, manganese, sodium, copper, zinc and magnesium.

 

Some plant species are able to concentrate particular elements in their bodies: Water Hyacinth (Eichhornia crassipes) absorbs large quantities of nitrogenous compounds. Such plants are useful in biological treatment of waste waters.

 

Nutrients in waters may vary considerably in composition and concentration, according to the natural cycle, the largest fluctuations occurring in rivers and creeks. The larger the water body, the more stable are the levels and so, in the aquarium long term stability is difficult to achieve.

 

Waters with little nutrient (oligotrophic) have less than 0.01 g of dissolved matter per litre and in these, the levels of plankton are restricted and the numbers of fish are low. Oligotrophic peat waters are in this category. Waters rich in organic matter (dystrophic) are usually low in dissolved minerals (particularly Ca ions) but high in humic acids. In such conditions of low pH and nutrient levels, characteristic peat-bog plants are found.

 

Waters saturated with inorganic nutrients (eutrophic) show mostly alkaline reactions and here plants with high nutrient requirements, such as Myriophyllum, Nuphar, Ceratophyllum, Elodea and others grow.

 

Only the halophytes (Najanus, etc.) can tolerate waters with high salinities.

 

In a following article, we shall examine the body structures of aquatic plants.