Guides - Plants In The Aquarium by Reginald Dutta.

Planting medium.
If the emphasis were solely on the plants themselves then all manner of special soils and fertilizers could be used. In the home fish tank, where the balance of all factors is more important than the plants, aquarium sand proves adequate for growth and for the maintenance of photosynthesis, i.e. the cycle whereby harmful carbon dioxide gases given off by the fish is broken down by the plants into oxygen and carbon, the oxygen going back to the fish, and the carbon compounds acting as fertilizers for the plants.

Points to watch.
The right balance between top light, sand, plants, fish, fish droppings, and foods, is very easy to attain - almost automatic in fact. An excess of light (natural, artificial or a combination of both) produces green algae. A sand depth of 1-2" is enough for a tank up to 18" tall. A plant selection that covers, in clumps, lines or clusters, about a third of the floor surface should normally serve a fully stocked tank. Not too sparse, not too overgrown; not too tall and trailing all over the water surface, but pruned back to below water-level, leaving just the small proportion to trail and float. If you mix the light and the dark greens, the tough big shade-giving leaf with the delicate, the fern with the grass and the reed, you can't go wrong. If it looks right then it probably is right.

Telltale danger signs are the white precipitate grains; dark patches in the sand immediately round the roots denoting too many harmful nitrites as distinct from beneficial nitrates, and a clean up is urgently wanted. A plant that sulks, changes colour, has stunted or deformed foliage is asking for a change of temperature or light, more room for its roots, or less heat below its roots. Pruning could help, so could a fertilizer pellet inserted at its base, or a liquid for its leaves. The bigger the leaf the more the plant tends to get sustenance from the foliage rather than solely from the roots. Mulm at the base or smothering the leaves is obvious; not so is incorrect pH or DH, but both are important. Planting too deep, i.e. below the crown, is asking for trouble.

If in doubt partly change the water, or alter the temperature by 2 degrees F depending on the season - in spring you raise, in autumn you lower. Similarly with the duration or intensity of the top lighting - in spring more, in autumn less as the plants tend to 'rest.'

Hints.
The lighter green the leaf, the more the plant tends to oxygenate. The bigger the plant the more difficult it is to transplant and the more likely to shed its leaves. So please don't be too greedy when buying 'that big one'!

Tall plants get stalky as the bottom leaves drop off; nearly always this happens with those that propagate from cuttings, rather than from runners sprouting below sand level from the parent crown. The cure is simple - nip off the lowest and stalkiest part, and replant the top bit that still has foliage; it will soon take root.

If the fish drive you mad because they keep uprooting everything, first make sure that they are not simply asking for more varied foods - eating the same unchanged stuff day after day, no wonder they chew the plants in desperation - then you can plant the cuttings not directly into the gravel, but first into porous and holed containers which are then embedded in. The holes in the containers should be big enough for the roots to spread out later. Decorative or plain flowerpots can be used, of course, but so can all manner of originalities - a clear, almost transparent 4" plastic tube cut to a short length just to protect the vital areas, leaving the roots and the top both free, is an example to start you on your own search. Ever tried using the gently fluorescent colored plastics that shed a softly flowing glow on to the plant and then reflect back to you?

Artificial plants.
Artificial plants have a place too. The old-fashioned sniff-sniffs recoil in horror from the idea, but others don't. Lovely colours, beautifully made; most useful in speciality situations and circumstances; easily blended and mixed with the growing ones - a fantastically wide choice. If used for marines the good old rule of pre-soaking in extra strong solution of salt is sensible; some plastics react to this treatment or even disintegrate. All plants should be free of metal wires or clips, and their glues should be non-toxic; there is little reason why you could not re-make your own sprays using the new aquarium rubberised sealers. It would be safe, and it could be original - would it shock you too much to incorporate pieces of wood, rock, coral and such like?

The joy of the aquatic trade is that it caters for all types - there are people who fall hook, line and sinker for the plants, and feature these above other aspects like fish, which are kept merely as fertilizers because of their droppings; with tank heights and tank lightings all sub serving the plants. For such enthusiasts the following additional data might help.

When transplanting dig out the plant, don't pull it out; take the surrounding soil too, if this is not possible then don't tear up, but having dug up, wash out the roots, all of them, ready to reposition as firmly based as possible later. A fertilizer tablet, or a lump of clay-like soil, the size of the top of your little finger, placed directly under the plant always helps, if you feel this is to be necessary.

The lighter green the plant, the more fast growing it is, the more food it needs, the more it sheds its leaves which tend to be small or thin and the more it needs a "rest" in winter. While thriving in summer the more it keeps down green algae partly by competing directly for the same "food" and partly because the algae cannot get a real grip on its relatively quick-changing foliage.

The slower-growing types can be left unpruned and unattended for a couple of years if you like - but watch out lest they slowly alter the water pH to suit themselves, to the detriment of the fish whole health then definitely plays second fiddle to plant growth. Often their leaves have a slightly bitter taste, or at any rate an unappetizing one, and fish seldom nibble into them, although often on them to get off algae and other microscopic growths attracted by the firm texture of the leaf.

In the tropics, many plants spend the dry hot summer exposed above the water, when they often flower and send up relatively big foliage. In the rainy seasons they tend to get flooded and to be totally submersed - the leaves then shrink, drop and lighten in colour; runners, plantlets and long thread-like shoots multiply. Under rapid transplanting both conditions are manifested - it's only a day or so from hot-moist Singapore to wherever your tank is!

The varieties available literally are ever changing, but the twenty-four that are illustrated are widely available, are well known, and are typical of the range in foliage, size, shape, colouring and propagation. All can be mixed and used in the home aquarium and all are either hothouse grown or imported from warm climates. The cheap, coarse, summer-only growths that you can clump out from the local ditch have not been included; they would normally die in your tank and foul it. For completeness, though, some of the beautiful lilies suitable for outdoor and indoor ponds have been shown, and are worth their place.