Hi.. I hv a heating elemnt of 1000 watts.. I want to decrease watts to 200 watts.. cn anyone tel me how I cn do it.. I want to use this heating elemnt in thermostat I my aquarium set... thermostat has volt of 220 n hertz is 50
I don't know nythng about ol this volts and hertz.. plzzz help me out.. in market no heating elemnt is available that has 200 watts...

So sorry about your lack of education in the English language.
Go to a pet store and get an aquarium heater. Do Not Attempt to use that element. You can get killed.