Algae is part of earth's amazing biosphere that we get to manage in an Aquaponics system. It's not a bad thing that you have algae in your system, but it can certainly cause some difficult problems if not monitored.
While algae is natural, a large amount is undesirable in an Aquaponics system. You will encounter some serious issues if your algae gets out of hand:
Dissolved oxygen in your system is one of the life sources for your plants and fish. Algae will consume this dissolved oxygen and leave very little for your fish and plants.
Algae will grow and multiply in ideal conditions and will eventually clump together and clog your system. You may experience fluctuations in your water flow and water may stop altogether.
Algae consumes CO2 in the system during the sunlight hours. Because CO2 is a weak acid, when it is removed from the system your pH rises. Then in the evening when the sun is not as intense, the CO2 begins to increase lowering your pH.
There are a few key tips that will durastically help your algae management. Implement these tips and wait a day or two and you will begin to see your water clear up.
If you haven't already implemented swirl filters or another form of mechanical filtration, now is a good time to start.
It is a good practice to properly paint your tanks (especially if they're IBC totes) before adding fish, but you can always add shade cloth to reduce the direct sunlight.