How to keep your fishtank water crystal clear

Good filtration

Use a filter that matches your tank size and stocking. Mechanical media (sponge, floss) traps particles and keeps water clear. Clean or replace media when it clogs, but avoid overcleaning — you need beneficial bacteria. See our filter comparison guide.

Regular water changes

Weekly partial water changes (e.g. 20–30%) remove dissolved waste and keep nitrate down. Use dechlorinated water at a similar temperature. Vacuum the substrate to remove debris without stirring up too much.

Don't overfeed

Excess food rots and clouds the water. Feed only what fish eat in a few minutes. Remove uneaten food after a short time. See how much to feed fish.

If water is cloudy

Milky or white cloudiness is often a bacterial bloom — common in new tanks. Wait it out; usually clear in a few days. Avoid overcleaning the filter. If it persists, check cloudy water and bacterial bloom. For green water, see green water fix.

Substrate and debris

Rinse new substrate before adding it. During water changes, hover the gravel vac above the sand or gravel to avoid sucking up too much. Stirring deep substrate can release trapped gases and cloud the water.

Quick checklist

• Filter sized for your tank; clean media when clogged.
• Weekly water changes; vacuum substrate gently.
• Feed sparingly; remove uneaten food.
• Use dechlorinator; avoid sudden changes.