Cloudy water is one of the most common guppy tank complaints, and it’s also one of the most misunderstood. The reason is simple: “cloudy” can mean different things. A bacterial bloom looks different to suspended debris. Green water is different again. If you treat the wrong cause, you can waste weeks chasing it. If you identify the type, the fix is usually straightforward.
1) White/grey haze (bacterial bloom)
This often appears in new tanks or after “too clean” overhauls. The fix is not sterilising the tank — it’s stability: moderate water changes, strong aeration, and time. Avoid replacing filter media.
2) Dusty particles (suspended debris)
Often caused by stirring substrate, overfeeding, or weak mechanical filtration. The fix is gentle substrate vacuuming, reduced feeding, and ensuring your filter has a way to trap fine particles.
3) Milky water after a big feed
That’s usually dissolved organics and micro-particles from food. The fix is smaller meals and removing leftovers. Guppies don’t need big dumps of food to thrive.
4) Green water (algae bloom)
Caused by excess light and nutrients. Reduce light duration, avoid direct sun, and keep nitrates controlled. Big chemical “fixes” can create swings — steady routines work better.
5) Cloudy after medication
Some treatments affect biofilms and bacteria, leading to blooms. Prioritise oxygen, watch ammonia/nitrite, and avoid stacking multiple treatments at once unless necessary.
Cloudy water usually clears when the underlying imbalance is corrected. Keep routines steady, avoid panic resets, and your guppy tank will return to clear, stable water.
