I have spent many hours in the last month raking algae and devising in my head ways to end the hopeless task or automate it, or make it easier.
Probably best tool is one that was pictured somewhere on the forum already a while back. It was a 20 foot or so steel post with a landscape rake type doo-hickey on the front all mounted on a front end loader. Drive as far in as you dare, put the bucket with attachment down and drag it back to clear much and algae at once.
A few things I noticed. The algae looks great after I rake, as the day turns to evening it must sink as it looks better and better. Then as the sun comes out the next day and water heats up it floats to the top and looks like I didn't make any progress at all.
Once at the top it is still tethered to the bottom so disturbing that tether is helpful. At least it helps the wind (if you are fortunate to have any wind, rarely do we here) push it around to one side of the pond and that makes it much easier to rake out. I put my small plastic boat in with a 6hp motor and stationed my son in the back to run the tiller. I put the front in the shallow up against my waist and braced myself as best I could. He floored the motor and swung the tiller this way and that way. It made a huge plume of water, mud, sediment, oak leaves and after a while really created a brown bloom behind the motor. Even a 6hp can really put some torque on the guy trying to hold the front of the boat especially if the boat is swinging form side to side.
But it really helped to go around and blast lots of muck and algae off the bottom as far as that prop could blow it. Then we made lanes back and forth and then around the perimeter to break up algae.
I think a seine net would work but would be tough to empty out every run of stringy alge. Heavy work with 2-3 people too i would think.
I thought of mounting a sort of 'V plow' with the point of the V at the front middle of the boat and the long edges of the V on a 45 angle out towards the sides. You could probably take a 55 gallon drum, cut in half the long way and fasten the two bottom ends tightly/closely together to be the point of the V and the other end spreading out on 45 deg angles. Then see if driving around would capture the algae in the drum halves? Probably would need holes in the drum to let water flow through as you go?
Another thing that makes it tough to scoop or trap algae is that when it is floating it tends to swirl around and escape. When you are raking a big patch the clumps want to spin around the edges of the rake as you pull it in. You almost need a rake that has a larger flat surface with multiple tiny pins that grab the agae in many places rather than relying on a single row of rake tines.
I saw a very neat pump system link on Pondboss where a large pump system just sucked a large volume of surface water and the algae just came with it. Probably loud, costly to run big pumps, but almost no effort till it comes time to empty the big vat of algae.
If others can provide links to the pump system, or the front end loader boom please post. I have tried the prickly rope technique and have not found the prickles coming off the rope to be strong enough to pull algae in that is tethered to the bottom. It might be a better system for gathering up floating oak leaves before they settle.
If there was a way to monetize the harvested algae there would be more inventions behind it.
My sister in law lives in Wisconsin and the local farmers have a strong desire to pay for lake weeds. Somehow they put the lake weeds on their farm land (not sure if it is chopped or processed or dried or if it just goes on in clumps/wet) and it serves as great mulch and fertilizer. In the community where they live they worked together to build a large automatic weed harvester. Think a large pontoon boat with big weed cutters about 5' below the boat and a conveyor system to feed the weeds up to a hopper on the back of the boat. All summer a boat runs around a VERY weedy lake and creates big lanes in the dense weeds. There is no way they can keep up with the entire lake but the lanes help with boat traffic in the common traffic lanes and the weeds are used by the farmer. The weeds pay for the cost of the boat and paying the operator and the farmers have not had to pay for fertilizer as long as they have weeds to put on their fields.
I'm confident there are great innovators and designers on this site if we put our ideas together.
