Clean deck before staining using 30 Seconds Outdoor Cleaner a hose & a bristle brush w/ elbow grease 

This is why you should buy a TREX deck from day one it truly is less in the long run ! ❤

I've had the same trouble with the algae. I had to do a TON of scrubbing. First I let it sit for about 5 mins, then tried 10..then tried 15..wet it down to scrub it. I got 90% of the algae and deep embedded dirt off, but not as much as I would have wanted it before I need to stain it. I'm thinking of hiring someone to finish it off for me. This deck was at least 20 years old and never cleaned. Tons of spotting and streaking..it was awful. For a product that boasted "no scrubbing needed" it was far from the truth.

I cleaned my deck with the 30 sec cleaner. My deck was a year old. I followed directions completely. Mine left white spots & streaks white like crazy. Then, I used a pressure washer, it didn't bring it up. So, I waited till it dried & actually hand sanded it. It still looks terrible!!

Pressure washing will take all that stuff off quick

Take the red tab off the nozzle.