How to Prevent & Treat Algae
Overview
A note on this guide: Algae is the #1 reason people get frustrated and quit this hobby. I'm going to share absolutely everything I know — every tip, every tool — so that you can have success with your own personal planted tank.
The truth is, algae isn't a complicated problem. Like most things, prevention and catching it early give you the best chance of success.
The Right Way to Think About It
Algae doesn't take over a healthy tank. It takes over a struggling one.
Think of it like a compromised immune system. The healthier your plants, the stronger their resistance — and the larger your margin of error when something goes slightly wrong. An extra feeding, a fish that died somewhere you can't see, a slightly off water change. Healthy plants absorb the hit. Struggling plants don't.
The 3 Variables
Every planted tank is controlled by 3 things: CO2, light, and nutrients. My general approach from day 1 is to take nutrients out of the equation entirely, keep light on the lower side, and run CO2 significantly higher than average. Fewer variables means less to troubleshoot — and less that can go wrong.
Prevention
Click any tip to expand it.
Treatment
Algae in week 1 or 2 is completely normal — don't panic. But if you're still dealing with it by week 4, it's time to move to active treatment.
When algae does appear, the approach is layered. Start with the least invasive steps first and add more based on how serious the problem is. Whatever combination you run, give it a minimum of 2 weeks — ideally 3 — before judging whether it's working.
If you want to pinpoint the exact cause, split test 1 change at a time. If you just want the problem gone, run the full framework for your severity level and let it work.