author(s)
Habiba Islam, Md. Alamin, Md. Sabbir Hasan, Subrata Mondal and Md. Mer Mosharraf Hossain

abstract
Green water indoor tank culture (GWT) of Tilapia with carp is an appropriate method for commercially producing of Tilapia in substitutional of different water bodies likes ponds, lakes, cages and reservoirs etc. that have environmental constraints such as land use conflicts, source of water, water quality and sub optimal temperatures, where a green house could be used to control temperature with minimizing the all possible constraints. This study showed that the high densities and feeding rates can be maintained through continual aeration and solid removal. Ammonia is removed by phytoplankton uptake and through nitrification on suspended organic particles within the water column. In the GWT the treatment process maintain good quality, reduce the need for water exchange and maximize water use efficiency. Phytoplankton (chlorophyta, rdodophyta, chrysophyta, cryptophyta etc.) and other organisms (Such as, zooplankton) within the water column are grazed on by fishes (tilapia, rui, catla, and common carp), thereby recycling waste nutrients and lowering feed conversion ratios. A Green Water technology (GWT) in indoor tank system for fish culture was developed in Jessore University of Science and Technology. The green water was produced and cultured in indoor tank using plant leaves, Joba (Hibiscus-rosa-sinensis), then Nile tilapia, rui, catla and common carp were stocked in indoor tank systems. Regular monitoring for health check, water quality check, temperature, siphoning and oxygenation with air-stone maintained adequately in indoor environment with available sunlight penetrations. The survival rate was 100%. No artificial feed was provided from stocking to harvest. Green water tank culture of tilapia with Indian major or exotic carps indicates that GWT has potential profit due to high productivity; average 150.99±0.5 gm/tilapia within 120 days and no fertilization and feeding costs, which makes green water tank culture appropriate for widespread application.