[header] How to do a water change in a freshwater aquarium [title] Pretreat a bucket of tap water. [step] Get out a clean bucket and fill it with water directly from the faucet. Follow the instructions on your water conditioner bottle and pre-treat the water prior to cleaning. 
The conditioner will make the water safe for your fish by removing dangerous chemicals and metal residue. [substeps] Go ahead and keep two plastic buckets, specifically for your aquarium use.