Copper sulfate is at best a temporary fix, and not a good one at that IMO, so I am glad you're not doing it
There are excess algae in your pond b/c there are excess dissolved nutrients in your pond. You can kill or filter out or hand-remove the algae but it'll just come right back as long as the same amount of nutrients are still present in the water.
If this is just a fairly thin "hairy" algal scum over the surface of the water, it may be fairly easy to fix. If however it is a seriously thick scum, or if there is little scum but the water is like pea soup, you probably have a serious nutrient overload and that can be real hard to deal with.
Plants help -- specifically, plants that take up nutrients from the water directly, not from their roots. But you have to be careful WHAT plants, because in a situation with excess nutrients THEY can often become a problem THEMSELVES.
I seriously don't recommend duckweed, it can totally blanket a pond and you will never, ever, ever get rid of it. (Yeah, it dies back in winter, but it will be back every summer. Really truly.)
If it is a
small pond, and I am only saying this because you are in Indiana not the South, you might consider buying a bunch of water hyacinth plants from a pond supply store (unfortunately not super cheap) and then rake them out and compost them at the end of the summer. Raking out and composting is CRUCIAL, you cannot let them die and rot in the pond, you need to REMOVE the nutrients they contain while you still can! Any survivors will be 100% killed off over wintertime.
You can also stock in some of the submerged, rootless or poorly-rooted pond weeds. There are a lot of kinds and honestly I've been out of pond ecology for long enough that I dont' trust my recollections of what's invasively dangerous in Indiana - you should look it up. You then rake/dredge out as much as possible of the pondweed in late August or so and compost it. But because you will never remove all of the pondweed, there is the possibility of IT becoming a problem in the pond, so you have to be ok with that. Note that these will not do well until the water becomes somewhat clear-ish, so you have to manually remove surface scum and tackle pea-soup water *first* before submerged plants will do much good.
The second big category of "things you can do" involves encouraging the excess dissolved nutrients to become bound in the sediments, and thus harmless from an algal-bloom standpoint. The nutrient that generally limits these blooms is Phosphorus. Phosphorus has the interesting property of being poorly soluble when oxygen is present, but staying happily dissolved in anoxic (low or no-oxygen) water. Ponds often go anoxic in the bottom water in summertime, thus preventing P from precipitating out and actually liberating *more* P from the sediments.
Thus the purpose of aerating a pond (which is a misnomer, really you are just stirring the pond so that it does not stratify and the bottom water doesn't go anoxic). A silly little fountain, scaled to the size of the pond, is the most commonly-used method. It really really does help. Highly recommend.
The final thing that you want to do is think about how nutrient inputs to the pond can be decreased. If this is a small ornamental pond, clean it out (remove any festering organic crud on the bottom) and don't fertilize plants where the runoff can go into the pond. If this is a big "real" pond, don't fertilize lawn or fields that are in the watershed of the pond, or do something to divert runoff from them if they 'must' be fertilized. If the pond attracts lots of waterfowl, try to discourage them. Etcetera.
In some cases, it's a quick fix, in others (like where the nutrient problem is really severe and the pond is quite large) it can be nearly-intractable. (BTW, the barley thing can be useful in some cases as a temporary measure, e.g. to try to clear water up a bit so that submerged plants can get going, but is not a good long-term "main strategy")
Good luck, have fun,
Pat, retired aquatic biologist
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