Algae in low-tech tank: what do I do?

You could try cutting back on your light an hour or maybe two a day. The Hair algae can be quite a pain to get rid of.
I'm guessing its all trapped up in your java moss?, In my case it loves to nest in there, and is quite a pain to clean. you can either pull it out and give it a good cleaning, try and swirl a toothbrush around in it,you can also try and spot treat it with excel, this is good at killing hair algae, or a combination of brush and gravel vac works too. are you running any Co2 in your tank? your plants may be missing either a macro nutrient or Co2 and algae is taking over. also, you may want to get a bunch of really fast growers in there.

I've got a similar problem 55 gal with 28 watts of 6700 K light about 14 hours a day. took out the aeration last night and added 1 2 liter bottle of DIY CO2 with an aquaclear20 as an impeller.

In the tank, I have Java Fern, Anacharis, Amazon Sword, 1 string of Hornwort, Mollies, a pleco, 3 panda corys, 2 clown loaches, and 5 otos. with so many bottom feeders/algae eaters, I have no idea how the algae is surviving. I turned off the light this morning so It only gets ambient light from the room and about an hour or two of sunlight in 3 areas about 4 inches in diameter (it sits in the basement under a window).

anything else I should be doing to kill the hair algae?

I find H2O2 works really well on hair algae as well. If its on your javamoss try and take it out of the tank and soak it in a solution of HO2O and water for 5-10mins.

I had problem with hair algae when I first set up my tank, I added a pair of rosy barbs and odessa barbs and they cleaned it all up within a few days. I think that the odessa barbs are smaller when full grown, maybe adding one might help. Good luck.