are phosphates to blame?

[Mephistopheles]

Whenever I do add water to my 30 gallon (including top offs and water changes) I seem to get a significant microalgal bloom. I tested the water source for nitrates and found none. I also tested it for phosphates. According to the color scale, I'm somewhere in between the .5-1 ppm range. I know that Ideally that number should be zero, but is this enough to trigger the algal blooms?

 

[HoopsGuru]

Any phosphates registering on hobby test kits are a major cause for concern and you are most likely seeing the result. With the algae bloom happening every time you add water, even if it is not the phosphates, it is reasonable to assume that something is amiss with your source water.