Sand bed turning gold

Got something new growing on my sand bed.  The sand bed is turning a bright gold/slightly brown color.  Haven't had this before.  I think it may also be starting on the glass.  Is this a type of algae that I've not had/seen before????   What causes whatever this is and how do I get rid of it????

 

The tank has been up almost 5 years.  75g with fish, live rock, snails, crab, and mainly some soft corals.  Paramaters have not changed recently:  temp @79-81, Am - 0, Nitrates - 10, alk - 3-3.5; ph 8.0, SG - 1.024, calcium 380-400, PO4 - 0.
I've been dosing with vodka for about a month now (2 ml/day).  Previously nitrates had been at @20.
I recently had a red slime problem and treated it with Red Slime control.  The 1st dose didn't take care of everything, so did a 20 g water change on 9/22 and then dosed a second time.  I had had the Red Slime control stuff for probably a year.  Dave H. told me that it has a shelf life.  I'm thinking that's probably why the 1st dose didn't take care of everything.
I had also been using the Algae Fix (Marine) from API for a couple of months (since the conference in Rhinelander).  I had a lot of bubble algae and other stubborn algae on my rocks.  That really did the job for removing the algae.   But its been 3 weeks since I dosed last.

 

No, it doesn't look like an algae

 

Phosphates are zero.  Never have registered any in my display tank, but I know that is not all that uncommon.  I did register phosphates several months ago in my quarantine tank, so I think the test is ok.  Bulbs were changed at the beginning of August.  Cleanup crew has not been depleted.  I have about 10-15 crabs and same number of snails.  The snails had been depleted at the beginning of the summer, but I replenished them over the last 1-2 months.