If your nitrates are between 5-10, it really is probably a lot higher. Your hair algae is consuming a high level or nitrates and phosphates to keep growing, that's why your tests are testing low. Getting a critter to take care of the algae may be fun to watch, but won't be effective. As the hair algae grows and consumes nitrates, phosphates and other nutrients, those things don't leave the tank, but they are locked up in the algae. When a critter eats the algae, those nitrates, phosphates and nutrients are released back into the tank. That's why people with refugiums and macro algae always thin it out and throw it away. Macro algae needs to grow to pull bad things from the water. Same with hair algae. You can do all the normal things like feed less etc, water changes, but the only guaranteed way I've come by to remove it quick and for good is bio plastic pellets. Like by two little fishes brand. Do a search to find out more about npx bioplastics. They are pure carbon and very effective in culturing bacteria which consumes nitrates and phosphates.