The official figures slate that the loss would be 10,000 fishes or 10 tonnes.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/telangana-probe-mass-fish-death-ordered
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/deccan-chronicle-telangana
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/telangana
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/lake-pollution
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/fish
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/hyderabad-t
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/heat-waves
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/biological-oxygen-demand-bod
[9] http://admin.indiaenvironmentportal.org.in/category/thesaurus/water-pollution