الفهرس 
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Abstract
The fertilization is one of the most important processes in fish farms management because of its great importance directly and indirectly in improves the fertility of water and increase fish production. Organic fertilization is the first pillar, which is working to reduce the cost of production of the unit of area. Fertilization by organic acids like humic and Fulvic is the most important sources of fertilizers
The Fayoum governorate is the most important governorates in the production of fish from aquaculture where investors are interested in following the latest systems and techniques in modern aquaculture.
This study was conducted in the Wadi Rayan, Fayoum governorate, Egypt, in order to study the effect of using humic acid fertilizer in the presence of two different densities of fish on water quality and the density of phytoplankton and zooplankton and then fish production for Nile tilapia fish in earthen ponds, as well as the selection of some isolates algae and measuring growth rates under the influence of different concentrations of humic acid in the laboratory. The study was conducted through applied and laboratory experiments as follows:
Applied experiments, which were on the pond through the design of two experiments as follow:
Eight earthen ponds were used in these experiments with an area of 2 feddan for each one. These ponds were randomly divided into 4 treatments with two duplicates for each one, (T1, C1, T2, C2). At first experiment, ponds of treatments (T1 as treated with humic acid and control C1), were farmed by tilapia fingerlings at a rate of 14,000 / Feddan. While for the second experiment the fish was farmed in treatments (T2 Treated with humic acid and, control C2) with tilapia fingerlings at a rate of 28,000 / Feddan.
Control ponds (C1, C2) in both experiments didn’t receive any fertilizer, while the use of humic acid fertilizer was done in both treatments (T1, T2) in both experiments at a rate of 3 kg / Feddan during preparation and then 1.5 kg per ton of feed during the study period which lasted 24 weeks. The water samples was taken weekly and samples of fish were taken monthly. At the end of the study, fish samples were taken for analysis as well as calculation of survival rate and growth rates of fish
Laboratory experiment
This study aims to find out effect of humic acid on dominant algae in region under study; they are Scenedesmus Acuminatus of green algae and chrocooccus minuts of blue-green algae, and that through a laboratory experiment containing five different concentrations from humic acid, 0.0%, 0.1%, 0.2%, 0.3% , 0.4% adding to media of alga then measuring some growth indicators such as the number of cellular and chlorophyll a for both algae. This experiment has been in laboratory phytoplankton - Department limnology - Central Laboratory for Aquaculture Research, Abbassa, Abouhammad, Sharkia.
The most important results are as follows: -
Applied experiments
Physical and chemical properties:
The results showed insignificant differences in water temperature between treatments in both experiments where it ranged between 24.5 - 32.8 °. The dissolved oxygen was between 5.4 to 8.9 mg/l. Sicck disk reading indicates increased in the fertility of water in ponds that have been treated with humic acid fertilizer than other control ponds with an average of 10 cm but in controls was 18 cm. As well as the results showed that the addition of humic acid led to decreasing the water alkalinity since control ponds (C1&C2) was higher than the treated ones (T1&T2).
Also, water salinity was found a significant effect due to the addition of fertilizer on (T1&T2). The phosphorus concentrations either total or dissolved was higher in ponds that treated with humic acid than ponds without the addition. Dissolved phosphorus was 0.21 mg/l in treated ponds while it was 0.06 mg/L in the other. It was a clear effect of addition of humic acid on the concentration of total phosphorus, where it was 1.05 while in the case of non-treated it was between 0.4-0.49 mg/l. Total nitrogen concentration was 1.26 in case of using humic acid, while in the other 0.36 mg/l. For the concentrations of nitrogen compounds, the results showed that the addition of humic acid led to a reduction in its concentrations in water, such as ammonia, nitrate, nitrite and all data was within the acceptable limits for the growth of the fish.