When the water gets warmer in the tanks - either due to increased sunlight hours or warmer weather - algae can become an issue. But it can be fatal to angelfish when an algae inhibitor is added to their water. Why? Because it can remove some of the nutrients what angels need to survive.
I pour a little into the cap so I know how much I am using, and then I pour it onto a tank sponge or cleaning rag set aside for tank use. I then wipe the inside of the glass with it. In my breeding tanks, I also use it to clean the bottom of the tank and for tank fixtures such as the intake.
If decorations become covered in algae, I'll remove the decoration and place it into a small bucket. I'll cover it in water and add algae fix to clean it.
A safe alternative to algae fix is plain old baking soda. A toothbrush can be used to brush off any stubborn algae.
I also have pleco's in each tank as well as mystery snails. They help to keep the algae down in a natural way, particularly my 15-inch pleco.