green slime algae? kinda blue-green in color?
is it very loosely blanketing the gravel or plants?
if you can remove a little of it, does it have a peculiar odor? kind of a strong, sweet, fresh cut grass smell?
if so, that' cyanobacteria...not a true algae but a bacteria. typcially caused by lack of nitrates in the water, or lack of water current.
10gallon planted tank...with how much light?
Are you testing for things like nitrates? phosphates?
Do you have CO2
I'm going to move this to the planted tank forum, so you can get all the answers you need.