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 merely the results, of plant damage.
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; valisneria, 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 CO2 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.
Following much research over the last few years it has been confirmed that plants produce certain substance 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 CO2 diffusion. Here both plants can take their carbon from the free CO2 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.
Recognizing and treating plant diseases
|Dark-green felt-like growth on leaves and stems||Algae infestation||See problem with algae|
|Clear, glass-like patches on leaf surface or tiny trails showing yellow or green||Attack by snails, loaches or sucking catfish||Remove the offenders|
|Brown holes on the outer leaves of newly planted echinodoras etc.||Die-back of existing leaves previously grown in an emersed stated||Remove affected leaves as new ones are produced|
|Sudden wilting of all plants in aquarium||Overheating due to the thermostat sticking||Adjust or replace the thermostat|
|Sudden wilting of cyptocolrynes||Cryptocoryne disease||None needed; the plants normally grow back again|
|Plants grow in a stunted manner||Insufficient level of carbon||Install a CO2 diffusing system, or increase its rate|
|Pale yellow foliage||Lack of iron||Commence the addition of a trace-element solution on a daily basis|
|Leaf tissue pale-green or yellow while the veins are dark-green||Lack of manganese||Add trace-element solution and begin the monthly addition of basic fertilisers|
|Certain plants begin to die back while others flourish||Biogenic decalcification of the water||Lower the pH value by increasing the rate of CO2 diffusion. Add an acidifier|
|Plants with red or brown foliage die back after planting||Suspect poor light levels||Increase the intensity of the lighting|
|Plants break off at grave level or shed leaves and stems||Black, polluted areas in the gravel or temperature in under-gravel area too low||Clean gravel and install an under-gravel heating system|
|Leafy pants become etiolated after a year or eighteen months of healthy growth||Possibly need to grow in an emersed state for a few months to invigorate them||Either lower the water level to allow the plants to produce emersed growth or replace with fresh plants|
|Tuberous rooted plants deteriorate after six months or so||Need to be rested||Remove from the aquarium and store in sand or peat at room temperature for a few months|