Effects of AquamatsTm on the Water Quality and Periphyton Growth in Nile Tilapia (Oreochromis niloticus) Fry Ponds
AC WEERA.SOORIYA and YANG Y1
Attempts were made to assess the effects of an artificial substrate named AquaMatsTm on periphyton growth and water quality in Nile tilapia fly ponds, located at the Asian Institute of Technology, Thailand. The experiments were conducted in twelve. 330 m3 ponds with randomized complete block design using sex reversed all-male Nile tilapia fry between 1.58-1.73 g in size. The stocking density was 30.3 fish m-2 in all the ponds. There were four treatments with three replicates each: (a) Non-feeding without AquaMatsTm, (b) Feeding without AquaMatsTm (c) Non-feeding with AquaMatsTm; (d) Feeding with AquaMatsTm.
Sixty-two periphyton species were identified on AquaMatsTm, among which 14 species belonged to Cyanophyta (blue green algae); one to Xanthophyta, 17 to Chlorophyta (green algae), 28 to Bacillariophyta (diatoms) and, two to Euglenophyta (euglenoids). Bacillariophyta were the dominant group with the largest number of species, followed by Chlorophyta, Cyanophyta, Euglenophyta and Xanthophyta, towards the end of the experiment. Total fouling solids increased towards the end of the culture period, whilst chlorophyll-a concentration on AquaMatsTm decreased drastically towards the end of the experiment. At the end of the experimental period it was observed that AquaMatsTm were fully covered with thick mud in all experimental ponds, indicating that it attracted the mud particles from the water column. Periphyton growth suppressed due to the deposition of mud particles on AquaMatsTm and it appears that AquaMatsTm cannot be used effectively in earthen ponds with Nile tilapia fry to enhance periphyton growth. The results revealed that the AquaMatsTm had no significant effect on water quality, both in feeding and non-feeding treatments (P>0.05).