Classification of plants

Plants are living organisms and as such have a complicated structure and metabolism. Each and every species has evolved over millions of years in particular habitats to which they have become adapted. Every individual niche in the environment has its own unique set of conditions and variables. It is therefore not surprising that the plants in our aquarium, having been uprooted from their home in a tropical stream, have problems in surviving in a home aquarium. Of course we do our best to provide them with all the essentials for their growth and survival but, with the best will in the world, we are bound to get it wrong sometimes, whether it be all the various species or just one for which the conditions are inimical.

Poor growth, rotting, discoloured or damaged leaves and roots are usually the result of an imbalance in the water chemistry. Plant epidemics which are pathologically caused by viruses, bacteria, or other organisms seldom occur in the aquarium. Attacks by insect pests are equally rare. Rotting leaves occasionally hold increased amounts of bacteria, but this is not the cause merely the results, of plant damage.

Mineral deficiencies

Often the abnormalities in the growth pattern will indicate a lack of a certain mineral. An element commonly showing an insufficient concentration in the home aquarium is carbon. This manifests itself by stunted growth of all or some of the plants; vallisneria, for example, may grow only an inch or so high. The plants produce runners normally but the progeny are equally dwarfed. Sometimes this can look very attractive but nevertheless is a tell-tale sign of deficiency.

Cabomba, hygrophila and sagittaria, as well as vallisneria, are particularly prone to this problem. This lack of carbon is often accompanied by an abnormally high pH value. The remedy lies in boosting the C02 levels by installing a carbon-dioxide diffuser system, and maintaining a lower pH level.

Lack of iron is another very common problem. In this case the leaf tissue is pale yellow. By contrast, lack of manganese leaves the tissue yellow but the veins are a dark-green colour. Strangely enough there may be adequate manganese in the system but it is inhibited by an oversupply of iron. This situation often occurs when iron-only fertilizers are used. A combination of trace elements in the correct combination will solve the problem.

Incidentally, an oversupply of iron will also inhibit the action of other elements, particularly phosphate. The iron is in fact reacting chemically with these elements to form insoluble compounds such as iron phosphate. It is for this reason that basic fertilizers, i.e. nitrate, phosphorus and potassium, should only be administered during water changes and trace-element solutions administered on a daily basis.

Alleopathy

Following much research over the last few years it has been confirmed that plants produce certain substances which inhibit the growth of other species in close proximity, a process known as alleopathy. This process may explain the poor performance of particular species which are notoriously difficult to grow in the same aquarium as certain others. Research is in its infancy and it will be some years before more definite knowledge is available.

Alleopathy probably plays a considerable part in certain species dying while others thrive. Sometimes this is the result of one plant exuding a substance into the water which is inhibitory to the growth of the other. Another situation is that which can arise when cabomba and elodea are grown together without the benefit of C02 diffusion. Here both plants can take their carbon from the free C02 in the water. When this is exhausted, elodea can use bonded carbon present in carbonates. This results in a biogenic decalcification of the water with a corresponding rise in pH of over 9. Cabomba is now at a disadvantage as it is unable to thrive at a pH greater than 7.5, and therefore begins to degenerate while elodea thrives as before.

Recognising and treating plant diseases

Symptoms Dark-green felt-like growth on leaves and stems

Clear, glass-like patches on leaf surface or tiny trails showing yellow or green

Brown holes on the outer leaves of newly planted echinodoras etc.

Sudden wilting of all plants in aquarium

Sudden wilting of cryptocorynes

Plants grow in a stunted manner

Pale yellow foliage

Leaf tissue pale-green or yellow while the veins are dark-green

Certain plants begin to die back while others flourish

Plants with red or brown foliage die back after planting

Plants break off at gravel level or shed leaves and stems

Leafy pants become etiolated after a year or eighteen months of healthy growth

Tuberous rooted plants deteriorate after six months or so

Cause

Algae infestation

Attack by snails, loaches or sucking catfish

Die-back of existing leaves previously grown in an emersed state.

Overheating due to the thermostat sticking Cryptocoryne disease

Insufficient levels of carbon

Lack of iron

Lack of manganese

Biogenic decalcification of the water

Suspect poor light levels '

Black, polluted areas in the gravel or temperature in under-gravel area too low

Possibly need to grow In an emersed state for a few months to invigorate them

Need to be rested

Remedial action

See Problems with algae, page 46

Remove the offenders

Remove affected leaves as new ones are produced

Adjust or replace the thermostat

None needed; the plants normally grow back again

Install a C02 diffusing system, or increase its rate

Commence the addition of a trace-element solution on a daily basis

Add trace-element solution and begin the monthly addition of basic fertilisers

Lower the pH value by increasing the rate of C02 diffusion. Add an acidifier

Increase the intensity of the lighting

Clean gravel and install an under-gravel heating system

Either lower the water level to allow the plants to produce emersed growth or replace with fresh plants Remove from the aquarium and store in sand or peat at room temperature for a few months

Species section

Aquatic plants embrace thousands of species. Many of those suitable for aquarium use are imported from the wild or grown in specialist nurseries that supply the hobby. Many other species remain undiscovered or have yet to be collected from areas that are inaccessible for geographical or political reasons.

This section of the book features a representative selection of 68 species, plus references to similar species of interest. The plants are presented in alphabetical order of their most familiar scientific name -usually the one by which they are known to plant dealers - followed by any relevant common names. The text entries are intended to give a clear and concise description of each plant so that the aquarist can easily choose suitable species for any particular aquarium or location. The reference value of the text is further enhanced by the five-point summary of environmental conditions in which each species will thrive.

All the plants included in this section are readily available and are capable of being grown under normal aquarium conditions. Really difficult species have been excluded, as have certain marsh and bog plants that, although frequently offered for sale, have a limited life when submerged in aquariums. In fact, it is surprising how many totally unsuitable plants - often simply houseplants - are incorrectly offered as aquarium plants.

When choosing plants for a new aquarium, select a few carefully considered types. This will avoid setting up a 'museum collection' of individual specimens of many different species arranged haphazardly in the tank. When buying plants, avoid those stored in dark, cold situations that may have shed their lower leaves or show signs of decay or brown spots. It is very difficult to revive a plant that has received such a severe check on its growth.

Descriptive terms used in the species section

elliptical j-shaped heart-shaped arrow-shaped arrow-shaped

Key to lighting levels

Subdued: Under 500 lux Moderate: 500-1000 lux Bright: 1000-1500 lux Very bright: 1500+ lux

See page 22 for guidance on lighting and a definition of 'lux'.

bipinnate

Lamina

Petiole kidney-shaped

opposite multi-pinnate

Petiole bipinnate opposite

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Responses

  • michael
    Is hygrophila capable of biogenic decalcification?
    6 years ago

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