Tiny Green Specks
 

In one of my plant-growing tanks, I noticed tiny green specks floating. These things are multiplying and are obviously some sort of plant. Size is no bigger than a small period at the end of a sentence. Many appear to be diads.
In the tank I have riccia and java moss.
Questions: are they spores or tiny seeds?
What do I do?

Algae?
Algae Blooms I presume?

These are discreet, of very uniform size, almost like near-microscopic duck weed. You could fit 100 of these spects onto the average duckweed leaf. Maybe some sort of algae I've never seen but more in common with duckweed in that it floats, it's discreet elements and it's multiplying like mad
I wondered about spores or seeds from something.