If it's thin and looks like hair waving in the distance, it's hair algae.
Until you can get your plants to out compete it, you can gather it with a toothbrush. Snag it with the head of the brush, and twist like you would gather spaghetti.
Definitely looks like hair algae to me. Manual removal, as suggested, is you best bet at the moment. You could try increasing circulation at that level of the tank, it helped me get rid of a batch that popped up in my 20L. If its not circulation, you have a nutrient/CO2 imbalance that ill have to be solved. It might be as simple as raising your light an inch or 2.
I also would like to put in more plants to help with the threads - gotcha on the light/nutrients. But I figure if there are more plants in the tank they'll use more light. No? Anyway, here's a picture of my tank, diatoms and all. Where can I put more plants and do you have any suggestions?
You could get some small foreground plants. Either a carpet or some anubias nana or petit. As for more plants using more light, that doesnt really apply, since each area has its own light. More plants will use more nutrients though. You could add some floaters that would help with nutrients and it would also diffuse some light.
Hi. I think it is thread algae. I got a good look at it when I was twirling it on the toothbrush. It's translucent when you're looking at individual threads but it was definitely green on the toothbrush.
I really apprecate all the help from you - this is something I've never seen.
I removed some gravel because I had too much today, and it kicked up a lot of particulate organic stuff that went right into suspension in the water. Hopefully a lot of it went into the filter. It tells me there's got to be a lot of it around the tank, especially around the plants which I dont vacuum.
I also reduced the photoperiod from 10 hours to 9. Hope that will slow the algae down.