Water sprite is ok if you really have it thick but most plants won't provide much cover unless they have a lot of tick leaves are the leaves actually hide the fish. I have used elodea with some success, also some hornwort. I have had better success with crypts if you can believe it. They get fairly thick and the leaves are strong enough that the adults can't just chase them through the stems. I also have really good survival rates with anubias and wisteria, agasin I thin because of the density and stiffness of the leaves and stems. The fry always hide right at the bas or around the stem and dart in deep in the plant if an adult comes around.
Density is really the key and any stem plant needs to have some good density. Most LFS have elodea/anacharis so get a couple bunches and if left floating, keep them together fo denser cover. It grows fast so trimming the less atrractive parts isn't too bad.