ive had afew picos and top off can be hard i think you should definatley put a piece of acrilic or hard plastic on top to help, if your useing a HOB filter try and put something in it to help with nitrates ect like seagel, phosgard or chemi pure they work good but i gess if your going weekly WC and dont whant any fish(but realy whats a tank without them
)you dont realy need it, also be carefull of heat! i had a 1g pico i started last winter but took down in the sumer because the water would get to 86 with the light on!