PopcornGirl, don't sell yourself short! While in a filled pool, the foamy detergents in such a product would 'mess with' the water, in an empty pool it could be applied and rinsed off and removed before the pool was refilled.
Speaking of which, Tark are you making sure that the pool won't float while empty - it's thaw and rain time and it would be a bad thing to read a post from you asking 'what to do about a floated pool'! Black algae can be dealt with in a full pool much easier than dealing with a pool which has floated out of the ground. If you don't have to worry about the pool floating, try what PopcornGirl and I advised, if there is a chance of the pool floating, fill it ASAP (you may be able to treat some of the areas with bleach before the water gets up there, but if not- settle in for a HIGH chlorine pool for a while) Please look at some of the black algae posts here to see what sort of FC you need to maintain to battle this. FWIW - straight 6% bleach should be 60,000 ppm (hope I got the math right ) and that should be more than enough to kill anything (if it stays in contact long enough)