I think that ID is incorrect. I have had this algae and I have had hair algae. This is not hair. I was never able to come up with the proper ID...
It feels slimy if you try to pull it out, right?
if it gets longer than about 1 cm. There might be some Oedogonium mixed int there and few diatoms. You need to deal with CO2, it's not to do with excess nutrients.............
Add more biomass, clean the tank more, watch the CO2 etc, Rhizo is a sign of a neglected tank.
FYI, Digsy nailed it with the CO2.
It's easy to kill, you can do an Excel treatment, a good cleaning, scrub etc, then add some more plant biomass if need be, cheapo plants till the others fill in, and add good CO2, reduce the light etc.
I have excess nutrients all day every day, I do not have this algae, thus I can easily and have for many years, handily disproven the "excess nutrients calims".
You cannot use a loused up tank as a control, by definition, such a tank is a lack of control, not a treatment tank.
You need a well run tank, then add "excess nutrients" and watch for a response.
The well run stable tank is your control and reference, not a "who knows what is wrong" tank like this one.
You also need to be specific, general things like excess nutrients #1 does not say what nutrient, nor #2 says what ppm or concentration is "excess".
If you do not know what nutrient, nor what concentration is required to induce the algae, you know very little about the mechanism of inducement.
I do not even need to know what is causing the algae here, all I need to know is what it is not
to show that excess nutrients are not a cause.
I have shown/demonstrated and repeated this so many times for so many years/decades now. Maybe I've just been lucky a 1000 X in hundred different set ups as have others?
I think not.