So to try to help -
For the algae,
-what do you have for nutrient export?
-Do you run any mechanical filtration? If yes, how often does it get cleaned/changed out?
-Do you have sand, crushed coral or gravel of any sort? If yes, then how is it or is it not maintained?
-What do you use for make up water?
-did the problem develop gradually over time, or just kind of pop up and then not go away?
For the fish;
-How long have you had the fish you have lost?
-Do some fish seem vulnerable and others are fine?
-Do you see any symptoms before losing the fish?
-Have you had any power outages?