I have not had much luck soaking algae sheets in any supplements. They tend to disintegrate on their own wo soaking, imagine with soaking them!
I would suggest that you follow Terry’s advise and think about expanding all your fishs’ diet…. You might want to try making up your own food mix which would include meaty as well as the algae with the addition of zeocon. You can food process fresh seafood such as shrimp, octopus, clam, ousters, etc., along with nori [algae sheets], etc., adding to this zoecon. Freeze slightly then cut into small portion size cubes, then complete the freezing. Then, you’re ready to go come chow time. The algae in this form is smaller and bite size. However, if you simply float sheets of algae in your tank, it will start to break up fast and become pollution. Unless your fish ravenously go for the sheets and can eat it up and chase it down in the tank within a few mins.
I have found that the fresh seafood, fresh algae along with the zoecon works very well for fish in your situation. Alternatively, however, there are many varieties of frozen foods sold for the hobby, including algae. You can also give these a try.
