It looks like it could be a thread algae, but it's hard to say. But you know what? It really doesn't matter. How about a rundown of your tank, how you're fertilizing and so on. Fixing that will resolve all algae in most cases. Prevention is the best medicine...
10 gallon tank
Eheim 2213 Classic
36 W Kit from AH Supply (8 hours a day)
Co2 Injection (3bps) with a ADA knockoff Glass micro-diffusor timed to turn on and off with the lights
EI dosing ( 1/8 tsp KNO3 , 1/32 KH2PO4, 1/32 tsp K2SO4 Mon/Wed/Fri )
( 1/32 tsp Plantex CSM+B Tue/Thus/Sat )
Water change On Sundays followed by 1ml of Excel
Note: I couldn't find 1/32 tsp measuring spoons.. so i use a Dash/Pinch/Smidgen/Nip set of spoons. I took 4 scoops of the Smidgen spoon and put them into a 1/8 tsp spoon and it seemed about right to fill it
I usually add the ferts late at night right before i go to bed the day before because I am just too tired and rushed to do it in the morning
I recently completed treatmeant of BGA with Maracyn before this stuff appeared. I thought it was Green Dust Algae because it started off on the glass. I wiped it off with a sponge.. and now it grows tangled between the HM, HC and on some of the other plants. I think i read somewhere that GDA only likes to grow on glass? So that leaves Hair or Thread Algae?
Guppies huh? Maybe i'll try picking up 2-3 at the LFS.. i think my dwarf puffers might kill/eat them though