Aquarium Algae: Causes, Types and How to Get Rid of It (Guide)

Algae is one of the most common problems in aquariums — especially for beginners. If your tank is turning green, brown, or covered in unwanted growth, you’re not alone.

The good news is simple: algae is normal, and it can be controlled easily once you understand why it appears.

In this guide, we’ll explain what causes algae, how to remove it, and most importantly, how to stop it from coming back.

What Is Aquarium Algae?

Algae are tiny plant-like organisms that grow in water. They appear naturally in all aquariums because they feed on light and nutrients.

In small amounts, algae are harmless and even beneficial. But when it starts to spread quickly, it becomes a problem — making your tank look dirty and sometimes affecting water quality.

Why Is My Aquarium Full of Algae?

Algae doesn’t appear randomly. It grows when conditions in your tank allow it.

Here are the most common causes:

Too Much Light

Light is the main fuel for algae.

If your aquarium light is on too long, or if the tank is exposed to direct sunlight, algae will grow quickly.

👉 Most aquariums only need 6–8 hours of aquarium light per day

Overfeeding Fish

Uneaten food breaks down and releases nutrients into the water — exactly what algae feeds on.

Overfeeding is one of the biggest causes of algae problems.

👉 Feed small amounts that fish can eat within 30–60 seconds

Poor Water Quality

High levels of waste (ammonia, nitrite, nitrate) encourage algae growth.

This often happens when:

  • Water changes are not regular
  • The filter is not working properly
  • The tank is overstocked

New Tank (Very Common)

If your aquarium is new, algae blooms are completely normal.

This happens because the tank hasn’t stabilised yet. As the aquarium matures, algae usually reduces on its own.

Lack of Maintenance

Skipping regular cleaning allows algae to build up over time.

Even a healthy tank needs:

Types of Aquarium Algae (Easy Identification)

Understanding the type of algae helps you fix it faster.

Green Algae

The most common type. It appears as green spots or a thin film on glass and decorations.

👉 Usually caused by too much light
👉 Easy to clean and control

Brown Algae (Diatoms)

Often seen in new tanks. It forms a dusty brown coating on surfaces.

👉 Very common in UK tap water setups
👉 Usually disappears as the tank matures

Hair Algae

Long, stringy green algae that grows on plants and decorations.

👉 Caused by excess nutrients
👉 Can spread quickly if ignored

Black Beard Algae

Dark, stubborn algae that sticks to surfaces.

👉 One of the hardest types to remove
👉 Often linked to poor water conditions

How to Get Rid of Algae (Step-by-Step)

You don’t need chemicals in most cases. Simple changes work best.

1. Reduce Lighting

  • Limit light to 6–8 hours daily
  • Avoid direct sunlight
  • Use a timer if possible

2. Clean the Tank

  • Wipe algae from glass
  • Remove affected decorations
  • Trim plants if needed

3. Perform Regular Water Changes

Change 20–30% of water weekly

This removes excess nutrients and keeps conditions stable.

👉 See: How Often Should You Change Aquarium Water?

4. Feed Less

Overfeeding is a hidden cause of algae.

👉 Only feed what fish can eat quickly
👉 Remove uneaten food

5. Improve Filtration

A good filter helps remove waste before it turns into algae fuel.

Make sure your filter:

  • Matches your tank size
  • Is cleaned regularly (but not over-cleaned)

Natural Algae Control (Clean-Up Crew)

Some aquarium animals naturally eat algae and help keep your tank clean.

Popular options include:

👉 Explore options here: Buy Live Fish UK

How to Prevent Algae Long Term

The key is consistency.

  • Keep lighting controlled
  • Maintain a regular cleaning routine
  • Avoid overfeeding
  • Do weekly water changes
  • Monitor fish stocking levels

A stable aquarium rarely has serious algae problems.

Common Mistakes to Avoid

  • Leaving lights on too long
  • Adding too many fish
  • Over-cleaning everything at once
  • Using chemicals as a first solution
  • Ignoring early signs of algae

Quick Fix Checklist

If your tank has algae right now:

✔ Reduce light time
✔ Clean glass and decorations
✔ Do a water change
✔ Feed less
✔ Check your filter

Final Thoughts

Algae is not a sign of failure — it’s part of the aquarium process.

Once you understand the cause, it becomes easy to control. Most algae problems can be solved with simple adjustments and a consistent routine.

👉 Explore more help here: Aquarium Guides UK
👉 Ready to stock your tank? Aquarium Fish for sale UK