Just block the light. Won't grow in the dark. That's why we use res covers.

Little bit of algae isn't going to hurt anything. A lot of algae should be cleaned up, as there are insects which will feed on it- and they're annoying. A whole lot of algae can present a "slip and fall" hazard- I reccommend swamp shoes and a squeegee.

Algae is just a fact of life in hydro- anywhere that solution is exposed to light, it'll grow. If you're using clear tubing for anything, it'll grow inside the tube.

Next time you're broken down, clean everything well.

You can slow algae down, but short of going to an algicide, it's tough to eliminate. If it's just a little algea on the top of your media- welcome to drip. Happens to everybody eventually.

If it's blocking your drippers, strip feed system down and peroxide it.