At my hatchery, we reclaimed rain water from our metal roof. Rain ran off the roof to gutters leading to 4 55gal drums at the 4 corners. Water from the drums drained to a 2500 gallon buried tank. Water from the tank was pulled through a 5-stage whole house filtration system leading to a several circulation holding tanks in the hatchery where the water was aerated until reaching the room's ambient temperature (The hatchery was heated instead of heating individual tanks). This water was used to replenish after filter back-flushing, gravel-washing, or just refilling the sumps after evaporation or bagging fish.
I still used filtered municipal water, when the holding tanks got low but, my cisterns saved me about 70-75% of my usual annual municipal water use.