[Randy Holmes-Farley]

I was wondering in a specific tank condition where nitrate has been zero and with high PO4, naturally there will not be enough nitrate to strike a balance to encourage Bacteria growth for PO4 elimination.

Yes, that is quite true. If nitrate were removed in a DSB or a denitrator, for example.

In this case, will the excess ethanol/volka, unused by bacteria be a source of algae growth?? Wonder what's the chemical composition of Volka & Ethanol, chances of these substance being a fuel for alage growth?

That's the part that I don't know: if algae can take advantage of ethanol in the water column. Still, if there is not enough phosphate for bacteria, then there won't likely be enough for algae either.