I heard that some people comb their hairgrass every week to get rid of the algae. I did not have problem with my hairgrass since keeping them for close to 2 years ago or perhaps I did not see them! =P
Do you mean algae at the bottom of the HG or near the tips. I think more likely the former, right? If that's the case, try combing it to see if it helps.
Cheers!
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