Cloudy or Green Aquarium Water: Causes and Fixes

Cloudy or green water is a symptom, not a disease. The colour tells you where to look, and in a warm place like Dubai it can develop quickly. Start with what the water looks like.

White or milky water

In a new tank this is usually a bacterial bloom while the biological filter establishes itself. It clears on its own over days if you do not overfeed and do not over-clean. In an established tank, milky water can follow a big clean-out that killed off bacteria, or a substrate that was not rinsed.

Green water

Free-floating algae need light and nutrients. The usual causes are too much direct sun, lights left on too long, too much food or too few water changes. A tank near a window is the classic case. Reduce the light, feed less and change water regularly. A UV clarifier can clear the water faster but does not fix the cause.

Yellow or brown water

This is often tannins from driftwood or decor. It is harmless to most fish and can be reduced with water changes or carbon in the filter.

Cloudy water that keeps coming back

• Overfeeding. Uneaten food feeds bacteria and algae.
• Overstocking. Too many fish for the filter.
• Dirty or undersized filter. Clogged media does not remove particles.
• Heat. Warm water speeds up every problem. See the chiller guide.

What to do first

1. Test ammonia, nitrite and nitrate.
2. Check that the filter is running and the flow is normal.
3. Cut feeding for a day or two.
4. Do a moderate partial water change.
5. Reduce light hours if the water is green.

When to call for help

If the water does not improve, if fish are gasping, or if there are signs of equipment failure, ask a professional to check the system. Our team is available 24/7 for emergencies, and visits are described in aquarium maintenance cost in Dubai.

FAQ

How long does cloudy water take to clear?

A new-tank bloom usually clears within a week or so. Longer than that suggests a cause that needs fixing.

Can I add fish while the water is cloudy?

It is better to wait until the water is stable and the parameters are safe.

For help with a tank, see our maintenance service or contact us.

Further reading: The nitrogen cycle (Wikipedia)