Algae Experiment

I have conducted several experiments with growing algae in my backyard. I wanted to see how algae would grow in different conditions. I first grew algae in one container in fresh water, and noticed it grew very slowly, unlike in normal pond water. I noticed the same later after separating the algae into two groups (both in fresh water, but to use one as a control group for later experiments). My hypothesis is that algae will grow differently in different types of water, and I want to grow it in pond water, fresh water (filtered) and tap water. I have already noticed that growth rates are slower in filtered water than in normal pond water (perhaps due to some environmental factor, e.g. other organisms, minerals, etc.). My main goal is to find the best way to grow algae and then look into it as a resource of energy and food.

Hypothesis: I thought that the type of water the algae was grown in (note that all algae had been originally growing in pond water) would affect the growth of the algae negatively.

Procedure: I noted the growth of algae in the original pond water (very fast, there is new algae appearing every few days), and then grew some in fresh, filtered water. 

Results: The algae grew much slower (no new algae appeared even after 2 weeks).

Conclusion: The growth of algae is slowed down when the type of water is changed from pond water to fresh water.

6/24/2014 update: I conducted the same experiment later and this time, I got results that opposed those of my earlier experiment, so the first experiment could have been conducted unreliably.