dark green algae-HELP!

[scary pool user]

I'm in a rental that has a small pool with a waterfall. About 3 wks ago we started getting cloudy water. We were told to just keep chlorine tablets in the floater, add a little algaeside and it should be good. Now the pool is a dark green color and it looks scary. I started testing the levels (never did that before) chlorine level is almost 0, Ph is 7.8. Have added Ph reducer, used a shock treatment and after a few days, it's the same again. I'm afraid to add too much of something. I also don't understand the concept of free chlorine. I really need someone to walk me through the steps. Please HELP! I'm desperate!! Will it ever recover?!

[GBUser]

If your pool water looks cloudy, it indicates a bad water balance (too much metal ion?). Make sure that your filter works well and use flocculant to treat the water while the pump keep running in the period.
BLACK ALGAE are usually on the pool wall and never let your pool water look cloudy. If you make sure that the pool has black algae, you can use chlorine tablet to rub all these dots of black algae. All ordinary measures never work.
You can try to use some special algicide or simazine.