One of the most attractive features of a tropical fish tank in the home is the potential it has for creating a beautiful underwater garden with a variety of exotic plants. The visual benefits are obvious but there are also important practical, but unseen advantages.
The aquarium is a microcosm of a natural watery environment and the part which the plants play in maintaining the healthy balance of the bio-system supporting the fish life cannot be easily achieved by other means. The simple function which we mostly understand is the way carbon dioxide is absorbed and oxygen is produced by the plants. As the fish are consuming oxygen and producing carbon dioxide they benefit from the process, as do the plants! However, there are more subtle and less obvious processes also aiding the water chemistry by the growing plants.
In theory an aquarium can be set up with plant and fish life in balance so that any form of filtration or aeration becomes unnecessary, but the low density of fish life which would be essential for such a system would not make the most of the aquarium’s potential. So, various forms of filtration and/or aeration are almost invariably used, but the “icing on the cake” can be provided by a good growth of plants and usually results in better colours of the fish along with improved all-round health, quite apart from their attractiveness. Some fishkeepers complain that they cannot grow plants at all, whilst others complain that their plants grow wildly and are having to be constantly pruned back. The failures are almost always attributable to an incorrect light source – either the type of lighting or the length of time it is on in the day, or the lack of feeding of the plants. Conversely, the over-successful growers might have an excess of both light and even possibly plant food. A balance between the two has to be achieved. Every aquarium is individual in its performance and there cannot be a simple rule of thumb to guide the fishkeeper, but general guidelines can be given and adjusted a necessary.
The depth of the aquarium is sometimes an important factor when lighting is being considered, as the fall-off of the lights’ intensity as it penetrates the water from the surface to the bottom is surprisingly severe. The average water depth of 12″ to 15″ will usually present few problems if the lighting above is from a single fluorescent tube, especially if it covers pretty well the full length of the aquarium and is a suitable spectrum (i.e. colour corrected or the newer coatings specially developed for aquariums). If greater depths are involved then it might be necessary to have more than one tube in order to increase the penetration capabilities of the light. Use of a Aquarium Reflector above the light tube will increase the light being reflected downwards.
Some confusion is often experience through the term “Gro Lux” applied to a well known form of fluorescent light widely used in aquariums. The name suggests that this light will grow plants luxuriously but it has to be realised that the tube was developed initially to grow horticultural plants where there was air between the light source and the plants. When water is between that source and the plants the spectrum changes somewhat. Also, the light level from this type of tube is relatively dull, and we have found that it is not the best tube for aquarium plant growth, although, of course, it does flatter the colours of the fish and will continue to be popular with some fishkeepers because of this factor.
The new high intensity tubes, such as Triton and Power glo, have an excellent spectrum and a light output almost twice that of a conventional tube. It scores in terms of rendering the fishes colouring beautifully, stimulating plant growth effectively, and having the intensity to penetrate to the bottom of most tanks adequately.
Feeding the plants is something which comparatively few aquarists seem to do, yet it is as necessary to feed the plants properly as it is to feed the fish well if you want to get the best from them. It is true that the fish waste will go some small way towards feeding the plants but this in itself is nowhere near sufficient. Liquid foods applied to the aquarium water on a regular basis are the most popular types. There are also tablets which can be inserted into the gravel adjacent to larger plants, and other forms of plant fertilisers available. Many aquatic plants rely on their root system primarily for anchorage and will extract much of their sustenance from the water, but others benefit from having something more than bare gravel around their roots. Such plants will do better when a section of peat plate is set beneath them, or may even be grown in a small pot containing a potting composts buried in the gravel. Putting a layer of loose peat all over the bottom of the aquarium before placing the gravel on top has its disadvantages. Such a method cannot, of course, be used with sub-gravel filtering systems. Also, with certain species of fish it will be found that they can dig through the gravel until the reach the peat layer and it will then be released into the water making it brown and messy. Also when pulling out any plants the roots will drag some peat with them and having broken through to the surface more fish digging is encouraged. So applied and controlled feeding is the better option.
Genuine underwater plants should thrive and propagate in the well managed aquarium, requiring pruning and thinning from time to time. But there is an interesting selection of plants which adapt to underwater life to varying degrees and for decorative purposes should not be overlooked. Such plants might be compared to annual bedding plants in the garden: They are planted out to last a “season” during which time they are pretty and pleasing, but at the end of the season they are best discarded and replaced. Some of these are bog plants and will be rather longer lasting than others which are more properly terrestrial plants often seen on the window sill rather than in the aquarium!
A frequent complaint is that the fish eat the plants. There are certainly some species which are vegetarian and eat them simply for food, and there are others…notably the larger cichlids…which just pull them up as part of their general tank rearranging habit. Some fish use plants to build their nests and the lovely Dwarf Gourami is one such species, sometimes seen ripping bits off plants to bind its floating nest together. But in the main the fish will not trouble the plants if the diet is sufficient. Usually it is not that they are lacking a vegetable element in their diet but more often it is because they are being offered the same dry food day after day, feed after feed, and they are bored with that. Those fish that are fed thoughtfully with a varied diet, including frozen and/or live foods, rarely become destructive of plants, and other vices like bullying or fin-nipping, may be minimised or even eliminated.