Hi Kitkat,
It sounds like you have a good idea for a project, and I think you are asking for help to get started. First, it will be helpful if can read more background information to learn more about your topic.
The science buddies website explains the importance of doing background reading. You need to think of questions about your topic and become an expert in the subject you will be studying:
https://www.sciencebuddies.org/science- ... plan.shtml
To get started, you need to find out about fertilizer and algae.
First lawn fertilizer usually contains high levels of the element nitrogen, which is essential for plant growth.
http://www.agr.state.nc.us/cyber/kidswr ... trient.htm
http://aob.oxfordjournals.org/cgi/conte ... t/96/5/871
http://hortipm.tamu.edu/ipmguide/nutrient/nitrogen.html
Algae are plants that grow in aquatic environments, so you need to know more about algae. For your project, you will need to pick one of the 300,000 varieties of algae to study:
http://hortipm.tamu.edu/ipmguide/nutrient/nitrogen.html
http://en.wikipedia.org/wiki/Algae
After your background research is done, you need to think about your experiment, and the science buddies website has a good guide for the basic steps:
https://www.sciencebuddies.org/science- ... thod.shtml
Please try to go through this process and ask a question that you will be able to answer with a carefully controlled experiment. Let us know if you have any questions.
Donna Hardy