Clean your water tank thoroughly once a week. Scrub all of the sides and bottom of the tank, in addition to any water features. You can clean the tank with a simple scrub brush and warm water. You don't need to use an algaecide to kill moss in the tank.
Change the water immediately after cleaning. This will prevent loose moss spores from clinging to the tank and growing again.
Move your water tank away from direct sunlight, if it can be moved. If it can't be moved, then use a curtain or shade to prevent sunlight from reaching the tank. Moss will thrive if given adequate sunlight.
Don't add additional nutrients to your water tank, unless a particular aquatic plant is suffering and requires fertilization. Also, don't feed your fish food with elevated levels of phosphorous or nitrogen. The presence of fertilizer and any undigested food with those nutrients will encourage moss and algae growth.