Cloudy water and bacterial bloom

What a bacterial bloom is

A bacterial bloom is a temporary explosion of free-floating bacteria. It often appears as white or gray cloudy water, especially in new tanks or after major cleaning.

Common triggers

• New tank startup.
• Overfeeding and excess waste.
• Deep substrate disturbance.
• Large filter/media changes at once.

What to do

1. Test ammonia and nitrite immediately.
2. Reduce feeding for 24–48 hours.
3. Do partial water changes if parameters are unsafe.
4. Keep filtration running and avoid overcleaning media.
5. Be patient: many blooms clear in a few days to two weeks.

What not to do

Avoid repeated full cleanouts or frequent full media replacement. Those actions can make instability worse.

Keep learning

Stable aquariums come from consistent testing and patient stocking. Continue with our water parameters guide, how to cycle a tank, and combining fish safely. For logging and strip scans, see App-aquatic.