Tell me about algae - how big of a problem is it?

[Chucker]

I built some new SWCs this year using clear plastic for the water reservoir. They will get some sunlight on them, so I wrapped them in black duct tape cause I was pretty sure I don't want algae.

But I'm still curious. How bad is it to get algae growth in your water reservoir? Does it take all the nutrients from your plants? Does it limit water movement in the containers? Anyone with experience, please share.