EFFECT OF GYPSUM TREATMENT ON WATER QUALITY PARAMETERS AND FISH PERFORMANCE IN FERTILIZED POLYCULTURE EARTHEN PONDS
Nabil A. Ibrahim
WorldFish Center, Regional Center for Africa and West Asia, Abbassa, Abou-Hammad,
Sharkia, Egypt.
Received 5/ 11/ 2012 Accepted 4/ 12/ 2012
Abstract
This experiment aimed to study the effect of agriculture gypsum treatment in aquaculture ponds (to raise water total hardness) on the physico-chemical and biological parameters of pond water and fish performance in a polyculture system. In order to achieve this goal, twelve 0.1-feddan (0.1-fed.). earthen ponds were randomly assigned for three treatments and control each with three replicates, ponds were treated with sufficient gypsum amounts to raise total hardness from 210 ± 13 mg/L as CaCO3 (control) to approximately 300, 380 and 450 mg/l as CaCO3 for I, II and III treatments respectively. Ponds were stocked with blue tilapia, common carp and silver carp in a polyculture system. All ponds were fertilized weekly with the same amount of superphosphate (40 kg/fed.), urea (20 kg/fed.) and chicken manure (35 kg/fed.). All fish were fed with artificial fish feed 25% crude protein at 50% of satiation level. Water samples were collected biweekly and analyzed for some water quality parameters (turbidity, temp., pH, SD, EC, DO, TH, T.Alk., NH4, NO3, TAN, OP and TP. and monthly for microscopic enumeration and classification of phytoplankton, zooplankton and chlorophyll “a” measurements. The results showed that gypsum treatment decreased the turbidity gradually by 54%, 53% and 72% for the I, II, III treatments respectively, pH values were lower in gypsum treated ponds than that in control ponds. Water quality parameters were however, within the favorable range for freshwater fish in all treatments, treated ponds had higher abundance of green algae and also zooplankton composition was of high quality especially rotifera and cladocera (small sized species) which is a good index for fish nutrition compared to control ponds. Fish production at harvest in the treated ponds was 1519, 1292 and 1469 kg/fed. for the I, II and III treatments respectively compared to the control ponds (1090 kg/fed.). An economic evaluation was carried out to compare the profitability of using different quantities of gypsum (i.e. different hardness) which declared that the net return of the treatments follow this sequence, the I, III, II treatments and then control (3563, 2620, 2132 and 1183 LE/fed. respectively), the I treatment had the highest relative rank followed in a decreasing order by III, II and control respectively.
Keywords: Gypsum treatment; Turbidity clearance; Water hardness; Polyculture system.
