Can anyone tell what this is?

[Peepers]

So my tank is probably about 4 months old. Still having some issues with nitrates. About 40. But I had a ton of what I'm sure was cyano. Reddish purple. Bubbly. It's slowly going away, and not coming back as fast so it seems things are getting more settled. But on my sand bed, if I go long enough I start to see a red purple tint starting and I get these stringy things coming from sand bed. Anyone know what this might be?

 

[VB313]

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[Peepers]

Video isn’t working

 

[Bret Brinkmann]

Looks like cyano still. Cyano can get stringy sometimes. Keep up with what you are doing since it is getting better but remember to not let your nitrates and phosphates bottom out or you run the risk of getting dinos. A good range is 1-5 ppm for nitrates and 0.10-1.00 ppm for phosphates. Some people go higher on the nitrates but the phosphates tend to be best left in a more narrow range in terms of algae control.