The Environmental Agency recommends the use of barley straw for the PREVENTION of Algae growth in lakes and ponds, not so long ago I was involved in using barley straw to combat a blanket & bind weed problem in a boating lake fed by land drains. the following pointers may be useful.
1. The straw needs to be added to the lake before the problem arises. We used to add ours around mid February as it needs 4 to 6 weeks to start breaking down properly. It acts by inhibiting algae growth not destroying existing so if you are to late deploying you will need to remove it mechanically (damn hard work!)
2. The bales need to be broken up to allow the water to circulate throughout the bale, if you don't do this the centre of the bale can stagnate and can actually make the problem worse. (place them in loose chicken wire or the posh reusable version plastic mesh) http://www.componentforce.co.uk/category/410/protective-netting-standard
3. Add flotation devices (we used pop bottles) to the bales to keep them on the surface of the water as the straw becomes waterlogged.
4. Dosing rates are quite critical and can be found out by trial and error, an Environment Agency article gave typical dosing amounts, which are repeated here, this may not be practical for very large lakes.
https://njaes.rutgers.edu/pubs/fs1171/Pond-Lake-Mgmt-Using-Barley-Straw-to-Control-Algae.asp
5. The breakdown of the barley adds minute amounts of chemicals to the water which would appear to INHIBIT the growth of ALGAE, please note that despite it's name Blue/Green Algae is considered a bacteria and not an Algae.
Dyes may also be used and will help to inhibit the growth of horticultural weeds as well this is perhaps the most useful article on it's use within recreational lakes
http://www.maidenheadsc.org.uk/main/images/downloads/dye%20use%20in%20weed%20management%20-%20very%20final.pdf
I hope this helps