When it gets hot especially during the summertime, you might see green stuff growing inside your filtration system. It would most likely be algae and it is very hard to prevent it. First of all, Adya Clarity water is filled with minerals which to the algae are nutrients. Second of all, algae spores are present in your water most of the time.
What you could do is, make sure that the Gravity Filtration System is away from direct light or heat sources. Some clients have tried wrapping the tank with paper to prevent light from shinning directly onto it. Others have suggested adding a couple of drops of grapefruit seed extract into the top tank which seemed to work exceptionally well.