Start reading up on cyano-bacteria and get some physan20 for clean up.
algea needs light and at first that is what is looks like but no green color. The more it looks like snot kind of light brown almost no color the more it sounds like cyano-bacteria.

It will choke off the roots and cause root rot. We cleaned up enough to barely save a harvest. Once it starts you will need the physan20, it's the only thing that will clean it out of your system. Chlorine and peroxide willnot take it out completely. The stuff makes a bio-film that embeds into plastic quite easily.