Filled the tank, chose the method

After cleaning the algae with chlorine I filled up the tank once again. I have done this a couple of times however I have learned my lesson, and because I don't want to have to do this again, I followed my brother's idea of covering the tank up, I am still deciding on which option is better, if a piece of wood or a piece of fabric. Each option has its pros and cons. the wood is stable but it requires more work in order to fit the tank, the fabric in the other hand is less stable and could be blown away by the wind, but it is easier to manage. After reflecting I chose to use fabric, a blackout old curtain to be specific. Because it is blackout the sun wont go through it and it is heavy enough to prevent the wind from blowing it away... as long as the wind is not extremely strong.