They work well at keeping algae to a minimum (if at all). Be advised that, if you have raccoon visitors to your pond at night, they love to chew the barley bales apart, making for a difficult cleanup. I keep one in my pond during the day, but remove it overnight.

I always keep 1 or 2 in my pond and they do a great job of sucking up algae and keeping my pond clean. My fish and I appreciate the help.

Excellent

I tried using algaecide and drained and scrubbed the pond while my poor fish were in a makeshift pond .
Nothing worked except these bales. They literally clear up the water in a day. My pond went from green STRING algae to crystal clear. They don't get rid of it, nothing does (that I could find) but they keep it under control makes the water refreshingly clear.
I make sure I always have some on hand!
READ THE DIRECTIONS or you'll be disappointed.

Once the warmer weather arrived it seemed as though the algae just grew so fast that I couldn't control it. I was using a chemical solution in the pond to try to control it, but it didn't appear to be helping at all. I had read reviews on Amazon and watched videos of others who have used barley straw, some successfully and some that it didn't work at all for them. So obviously I was skeptical about whether or not this product would remove the algae from my pond, not to mention I'd have to wait 30 days to find out if it would be successful. Let the photo speak for itself. In the photo you can see the BEFORE on the left taken on May 8th. The photo on the right is the AFTER taken on June 12th (about 35 days later). The barley straw in the back left in both photos (floating on left, then semi-submerged on right.) You can see the underwater pot on the right indicating the water has cleared up. I can see my fish again in the water! It does work. I'm a believer now. I should add that 2 loaves of barley straw are for a pond of up to 2500 gallons of water and my pond is around 2700 gallons.