Last week we had 2 extremely hot days in the Netherlands, and our pond water went from crystal clear to 1 big clump of green algae.
Its never been so bad!

The fish literally had no place to swim anymore.
Its a 1250 litre pond so you can imagine how much algae that is.
I removed a few buckets but am wondering if someone has a good tip on trying to prevent this stuff?

String algae?

I have hair algae in my tanks that are by south windows and have removed most of it manually and am adding calcium bentonite clay to see if it'll help.

Yup I think its string algae - its like a blanket of algae.

I have a small container pond outside, and I had a bad algae problem, too! I know this response is late, but I'm here trying to find a cure for my indoor tank - there's black spots forming on the plants (they're not real, but not plastic - kind of like silk plants) and they're in the tank with my 3 babies who are about a month old. anyway...

Did you find your cure? I use barley extract. It comes in liquid form. I found out from ebay that people use barley straw. Something about when the barley decomposes in the water, it naturally kills the algae. Anyhow, I couldn't find barley anywhere, except on ebay. Then I went to Petsmart, and they have it there! It worked instantly! My algae was tough, so I kept putting in small doses every other day, then moved to once a week (like the bottle instructs) but my pond has been free of algae ever since.

And it's harmless to the fish and plants. I hope you've already found a cure, but I'll post this just in case.