When Do I Change Water?

[vaishal867]

its been 3 weeks i dont no when to change water by the water looks crystal clear not cloudy or anything...should i take some part of water and add fresh?

 

[WILDER]

Need alot more info, on how long the tank has been set up, how many gallons or litres the tank is, which fish and how many, plus water stats in ammonia,nitrite,nitrate,and ph.

 

[Tokis-Phoenix]

Generally, its advised you do a 25% water change with dechlorinator once a week regardless of how stocked your tank is, but if its newly set up or is experiencing water quality issues or is overstocked etc you need to do more water changes. How long has your tank been set plus the other questions wilder asked?