Maintenance of the Aquarium
To maintain the aquarium is to keep the balance reached with the maturation of the filters, the growth of the plants and the healthy of the fishes. It is part of the maintenance the interference of the hobbista to feed the fish, to remove dead fish, to prune very big plants, to remove yellowish leaves and to maintain the quality of the water (cleaning the filters and the gravel to remove dirties and making partial water changes). The fish should be fed in agreement with its needs, but they should never receive food in excess, since to try to reproduce a natural habitat we have to remind that in the nature one of the daily fights of those bugs is to get its food, that it is rarely found in great amount, and not always it is available. The lack of food in the tank is less harmful than the excess, because that ends up dropping in the botton, and when it decomposes, it pollutes the tank. The ornamental fish can pass up to 7 days without receiving food. The very big plants end for covering the surface, hindering the penetration of the light, and so altering the balance of the fishbowl when harming the development of lower plants, which will not receive light enough. 
When there are a lot of shadow areas in the tank, the brown algae begins to develop, what is not bad for itself, but points to an alteration in the water. 
The yellowish leaves, as well as the excess of dejections and rest of food, must be removed so that they don't begin the to decompose altering the quality of the water. For the removal of the dejections, it is recommended to do partial water changes. The water to be restored should be treated and in the same temperature of that in the tank, so that the fish don't suffer a thermal shock. The best technique is to use a siphon and with it to jog the gravel layer so that the dirt is moved and suched outside the tank. Last, if external filters exist, those should be checked regularly to verify if some filter element should be changed or cleaned.
Doubts? Suggestions...
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