To determine whether or not you have an algae issue, the easiest way is to test the chlorine at night after sundown and then again in the morning before the sun hits the pool and see if you've lost any chlorine in that time. If you've lost more than 1 ppm, then you have something eating up your chlorine and the pool needs to be shocked. If not, then you know that's not the issue. However, this requires being able to do your own testing. In your case, if you have any doubt at all, I would shock the pool anyway just because your chlorine levels are way too low for your CYA level.After that, you're going to need to keep your chlorine at a minimum of 8 ppm to make sure the algae stays away.

I don't see any problem with using the lithium chlorine that you have--I've never used it, but I know that it's one of the most expensive forms of chlorine that you can use--I certainly wouldn't go buy any more of it, but I don't think it would be a problem to use up what you already have. After that I would switch to bleach.

Janet