Filling the tank for the first time

[Albertan22]

Well I'm almost there. My sump is mostly built and my stand is ready to be picked up tomorrow Plumbing will be my next challenge, but I've been wondering how bad it would be to fill the tank with water from the garden hose the first time around?

I have a 75 gpd RO/DI filter, so I could make up RO water, but the tank is 120 gallons with a 40 gallon sump (a lot of water and a lot of waste). If I'm gonna make that much filtered water I'll have to get it started sooner than later.