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|How to grow aquarium plants|
Sooner or later the aquarist gets the urge to create a beautiful underwater planted garden:
Easy - Buy some attractive plants and stick them in the sand.
Truth - Couple of weeks later all of them have rotted and melted away.
…So what went wrong?
Plants require light, nutrients, trace elements, C02 and substrate to grow.
Let's look at these issues....
A rule of thumb is to provide between 0.5 and 1 watt of fluorescent light per litre of water in the tank. So for a 2x1x1 tank holding about 50 litres, the minimum would be 50 x 0.5w = 25 watts, and better still 50 x 1w = 50 watts. Some plant varieties need more light while others do well even under low light conditions. Do not use incandescent lamps. These lamps will add unwanted heat to the aquarium which can raise the temperature to unbearable levels during summer, and they consume a lot of electricity with low light output. The only advantage is that they are cheaper than fluorescent lamps. With compact fluorescent lamps becoming cheaper everyday, use them if you can afford them. These lamps will pay you back in lower electricity bills and lush plant growth. Better results may be had by using two fluorescent lamps of different colour temperature. Use one bluish (white) and one yellowish (warm) lamp in a two lamp set up.
Plants need light in the same way as the sun provides daylight. The light must be switched on in the morning and switched off in the evening. 10-14 hours is the usual amount. Plants from the tropics need 12 hours even day/night, while plants from temperate regions are used to short days in winter and long days in summer.
So don't leave your lights on indiscriminately at night. On occasional evenings when you have guests the light may be left on for few hours extra to "show off" your aquarium.
Lights may be turned off for a few days to control algae outbreaks. A few days of low natural light will not do much damage to your plants but will control some types of algae.
Aquatic plants need the same nutrients as garden plants. Fish excretion provides the macro nutrients N,P,K, i.e. Nitrogen, Phosphate and Potassium. But plants also need iron, nickel, zinc, boron and traces of many others. These are not easily found by the plants in an aquarium. In nature most water bodies are very large or are constantly being replenished as in rivers. Such sources have all the nutrients for the plants. In limited aquatic environments like the home aquarium some trace nutrients are provided by regular weekly partial water changes.
Lack of macro nutrients will result in stunted growth, yellowing or even holes in leaves. These may be caused by very low fish load in the aquarium or too little water changes. Do not think of adding garden fertilisers, these contain large amounts of phosphates which will result in algae outbreaks, and excess nitrates will stress your fish.
It's best to add micro-nutrients only. Pre-formulated micro-nutrient solutions are available at aquarium shops. Do not overdose, or you may end up killing your fish. Follow instructions carefully and if in doubt ask a fellow aquatic planter for advice.
Carbon Dioxide (CO2)
Carbon dioxide (CO2) is essential for photosynthesis. CO2 in the water comes from fish respiration, or is dissolved from the atmosphere. Just as you need to aerate and circulate water from the lower levels of the aquarium for oxygenation, you need to do the same so that the plants get enough CO2. The amount of dissolved CO2 is not proportional to the amount of dissolved 02. These two factors are independent of each other. Proper aeration and circulation of water will ensure that requirements for both gases are met.
Increased growth of aquatic plants may be realised by injecting CO2 from an external source. This type of injection provides a method of controlling the pH (acidity) of the aquarium water and providing the plants with extra CO2 to stimulate growth. CO2 may be injected from a liquefied source (gas cylinder) or by a small fermentation unit. The gas cylinder method requires a lot of hardware and is not recommended for a casual enthusiast. The fermentation method may be easily made as follows:
Take a 1.5 or 2 litre plastic cola bottle, poke a hole in the bottle cap and fix an airline tubing to it, making sure that this attachment is air tight. Half fill the bottle with water, and add 1/2 cup of sugar and 1/2 teaspoon of baking yeast. The mixture should be fermenting within hours. The gas generated during fermentation is fed through the air line to the aquarium and dissipated through an air stone. This will last about 15 days and you will need to discard it when the gas output visibly decreases, and mix up a new batch. Use a non-return valve on the air line to prevent the water from getting sucked back into the bottle. Do not fill the bottle more than half way, or you may end up with the yeast and sugar mix overflowing into your aquarium.
Aquatic plants need an adequate substrate (sand) in which to root. The substrate should optimally be 1.5mm. to 3mm. in size. Too fine a substrate will result in anaerobic conditions for the plant roots - water will not circulate when the substrate becomes clogged with detritus, and the result is a black stinky mess in which the plants' roots will rot and die.
The depth of the substrate should be 5 - 10cms. (2 - 4 ins.). Some plants will happily grow in lesser depths, while others like the Amazon Sword plant need at least 8cms. of substrate. Its better to make an error on the larger size and have a deeper substrate where most plants will be happy.
Tips on plants
Select healthy looking plants when buying from local fish shops. Do not buy plants from aquariums where you can see small bits of plants and leaves floating - these plants are already disintegrating.
Plants can bring diseases and pests into your aquarium. Sterilise plants by soaking them for 10 - 12 minutes in a dilute solution of potassium permanganate. The solution must be light pink in colour.
Before planting, remove all damaged and dead leaves. Don't worry if the old leaves all die out at first - they will grow back in due course.
Some plants like the cryptocorynes are known to suddenly melt (leaves dissolve into paste) when the light levels are changed. They will grow back within a couple of weeks.
Some species of aquatic plants change their appearance according to light level and nutrients available. What is a giant plant in one aquarium will be a midget in another aquarium.?
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