If you are not using RODI water, your headed for a long and fustrating time.
Please provide some tank information in your signature. This will help others help you.
Everything starts with water quality. Typically, tap water will fuel all kinds of unfavorable algae. In your case, expect to see the following:
1. Diatoms (brown algae, dusting on glass and sandbed)
2. Cyanobacteria (blue-green algae covering sandbed and rock) This occurs in any high nutrient tank
3. Hair algae
You will ALWAYS have one form of algae in your tank, but you must make conditions favorable for the more desireable types such as coraline algae.