Algae bloom in an aquarium: the real causes and a 7-day fix plan

Quick answer

Algae blooms are usually caused by too much light, too much food, or poor maintenance. Reduce light to 6 hours/day, feed less, do a 25% water change weekly, and remove algae manually. Add easy plants to compete for nutrients and keep nitrate under control.

The simple truth about algae

Algae is a symptom, not the enemy. It shows your tank has excess energy (light) and nutrients (waste).

The goal is not a sterile tank. The goal is a balanced tank.

The 7-day fix plan

Day 1: remove what you can

• Scrape glass and remove visible algae.
• Siphon debris from the substrate.
• Clean decor gently in removed tank water if needed.

Day 2: reset the light

• Set a timer to 6 hours/day.
• Avoid direct sunlight.
• If you have a bright plant light, reduce intensity or raise it.

Day 3: fix feeding

• Feed smaller portions.
• Remove uneaten food.
• Add a fasting day each week if you tend to overfeed.

Day 4: improve water quality

• Do a 25% water change.
• Test nitrate. If it is high, increase change size or frequency.

Day 5: add competition

Easy plants help stabilize the tank:

• Anubias, java fern, crypts
• Floating plants (great nitrate sponges)

Day 6: check filtration

• Confirm good flow and surface agitation.
• Rinse filter sponges gently in removed tank water.
• Do not replace all media.

Day 7: repeat and monitor

• Keep the light schedule.
• Keep weekly water changes.
• Track nitrate and feeding.

What not to do

• Do not overdose algaecides as a first solution.
• Do not turn lights off for weeks (fish and plants need rhythm).
• Do not add “algae eaters” without knowing their adult size and needs.

FAQ

Is brown algae normal in a new tank?

Yes. Diatoms are common in young tanks and often fade as the tank stabilizes.

Do snails and shrimp solve algae?

They can help, but they are not a replacement for light and nutrient control.

Why does algae keep coming back after I clean?

Cleaning removes the visible algae, but the cause is usually still there: too much light, too much food, or too much waste.

Next step

Want a fish recommendation that fits a low-maintenance setup and reduces algae risk?