Marisia - Maros Megyei Múzeum Évkönyve 32/1. (2012)
Zoology
Gabriela GRIGORAS, Marcela ROSCA----------------------------------------------------------------L1----------------------------------------2------------Fig. 8: The cumulative effect of temperature, light and C02 content on plants growing. Various combinations of factors with different levels lead to different rate of plants growing. The aquarium substrate: chosen type, the nutrients content, convection waves. The cultivated aquarium plants are both submerged species and marsh adapted species. In the first group, nutrient absorption occurs through the root system as well as through the leaves surface area, their root system has a mainly fixing role. In contrast to this, the marsh plants develop a strong root system that extracts most of their nutrients demands from the substrate. That why, a special nutrient enriched substrate and a mathematical methods of water fertilization are essential for good results in plants growing. The aquarium plants originate from tropical and subtropical areas where there is a big diversity of the soils but the laterite-containing substrates (red soils) are typical. These kinds of soils are identifiable by their red color and are poor in nutrient content, rich in iron/aluminum oxide, a pH value within the acid to neutral range. The rapid mineralization of the organic matter as well as the generally low water conductivity promotes quickly absorption of the released nutrients by the plants. The plants species from these ecosystems with weak acid to neutral soils are ecologically stenotopes having a reduced adaptive potential to the aquarium water pH and hardiness. In contrast, the plants species from typical aquatic living environments with alkaline soils (such are the great African lakes) display a large tolerance range and they can easily be cultivated into aquarium. Having in view these considerations regarding the aquatic soils types from tropical and subtropical areas, the following features of the aquarium substrates were allowed in building of aquarium environment: • Low or null content of decomposable matter (e.g. humic acids). • Weak acid substrate. • The lower substrate layer is a clay type enriched with essential nutrients such as iron, minerals and trace elements that are gradually released to the plants. • The upper substrate layer has a dark color (allowing the heat absorption generated by light bulbs), coarse grained structure and low density (with an important role in the water and nutrients circulation, substrate aeration, adsorption of excess nutrients, allows a large colonization area for pollutant-adsorbing bacteria and favors negative phototropism of plants root system). • A good aerated substrate guarantees an optimum rate of microbiological processes that develop at this level. 124
