How to grow, and spread algae in my tank?

The best way to grow algae is to put the fish tank in a lot of light e.g. in the sun or get a light for it. Live plants can also causes a lot of algae to grow. Don't put fertilizer in your fish tank because it can be very harm full to the fish unless it is specifically designed for fish tanks. But i cant work out why you want algae to grow because it grows up the side of the glass and can be a pain to get rid of. It also makes your fish harder to see.

I would purchase a small grow light - Check out Spray-N-Grow Hydroponics

You can go to your local pet store and buy these little algae discs in a bag. you just drop one in every 2 days.

Algae growth results from a buildup of organic substances and adequate light. The best way to grow algae is to purchase plant food meant specifically for aquarium plants and an aquarium light. The light does not need to be high intensity; however, green algae only grows with high light intensity. If you have enough nutritious molecules in the tank, without adequate light, brown algae will grow. Your marimo ball may influence the growth of algae in your tank, but not enough to prevent any algae from growing. Algae will most likely not grow if you don't have sufficient aquarium lighting.