I often (always?) get a weird thread algae in my own shrimp tanks as the "3rd wave" after diatoms and GH, seems to come around 4-6 months in or so. Mine grows longer than that but is similarly lightly pigmented for lack of a better term. Seems to grow on the sponge filter and brightest spots. If it's the same thing I see pretty regularly, it's not too hard to manually remove the bulk of it and it eventually seems to wane if you keep things clean. I've not found anything that will eat it, it was quickly destroyed by Excel but I avoid using that in shrimp tanks. Peroxide may be worth a shot and it loves bright light.
Nothing good happens fast in an ecosystem.