Black Algae on Concrete
 

What is the best way to remove this and is there a way to prevent it ?

Buy 30 second outdoor cleaner at HD or Lowes, hose attachment sprayer. Leave on for at least 10 minutes to work in shade, rinse. Twice a year maintenance.

Yes, that works and I've done it with good results. Up north my concrete patio was very black on that concrete I used "Wet and Forget" it's about $35 for a small container, it doesn't work overnight but give it a few months and it will clean up the mess.

Yes, I have used wet and forget but 30 second is faster and significantly cheaper. There is a video on YouTube comparing outdoor algae cleaners and 30 second is clear winner. However, leaving it on for 30 seconds doesn't make since, just my opinion. I also use it on my house once a year.

You may be able to seal the driveway, but i would look into where the moisture is coming from and can it be eliminated. If you decide to seal, be sure it is correctly cleaned prior to sealing, and if you are doing it yourself, I would use the water based sealer, WITH shark grip added so you do not end up with a very slippery surface when wet.

it is mainly in the back along the sprinkler line

I agree the 30 second is faster and I used it 2 weeks ago on our white garage screens and some on the driveway. Wet and Forget is really pricey no dout about it.

Powerwash

Have you looked into adjusting the pattern of the spray heads, easy to do.

30 second cleaner is basically bleach … you will discover that after you ruin your shirt and pants…
Go with Wet & Forget it’s a conservative approach and works great…. Can you readjust a sprinkler head to avoid future problems? I use Wet & Forget on the house every 3 years …

I set up a garden sprayer with a 3:1 water to bleach solution and spray the infected areas. The spores will die and mother nature will take it away when it rains avoid getting on your lawn and plants.

We have small black spots on our vinyl siding. The chlorine-based "House Wash" sold at Lowes does a great job on the green algae but does not touch the black dots. Power washing doesn't handle it very well unless you focus the blast directly on it for a few seconds. With the numerous black spots scattered all over the house, this is not an effective way to treat the spots. Besides, the pressure washer damages the surface of the vinyl when used in that fashion.

My questions are: (1) does "30 Seconds" damage the vinyl surface? and (2) has anyone used "30 Seconds" on vinyl and was it effective?

Spray with White Ox and rinse off with hose.

A. Pressure Wash (Get an inexpensive unit like Sun Joe at Lowes).
B. No. ( Mold and Mildew vie for un-official Florida State Flower every day).

The black is probably just pollen that had fallen and decayed. That's what makes my driveway black, not algae. I find it easy to clean with an inexpensive pressure washer. I put some Simple Green in my soap tank, spray the driveway and then power wash it off. Takes a few minutes, but I save the money that I would have to pay someone else to do it. Some folks seal their driveway and say it makes it easier to clean.