Heck, hopefully by then you learned how to grow plants.
Yep, and I have you to thank for that.
But I learned to kill algae elsewhere. The two skills complement each other, rather than being mutually exclusive. Fix the root of the problem first if possible so it doesn't recur. Then fix the problem fast or slow. Your choice.
And there's always the odd problems like the clado in the java moss that nothing else will solve or prevent. Every tool and technique has value in the right situation. Keep trying new stuff!