I started my tank roughly 8 weeks ago and there is no sign of algae. Is this normal? Do I have to introduce algae to the tank? Right now my nitrate level is between 20-40ppm. Would algae lower this?
4 hours a day is not enough for fish either. What you want it to have 12 hour on and off cycled. For example on at 9am and off at 9pm. This keeps the fish's internal clock in sync, like us humans do. To make it easier you can even get a timer.
Why would you want algae? If you don't have otos or other fish that like algae, you should probably want to avoid algae. I have an algae problem right now, and it's very annoying.
Anyways, to get algae, dose potassium and phosphates. An excess of those nutrients will cause a huge algae bloom. That's what I did to get algae.