White gunk in NFT system

[mjmodel]

Built a NFT system and got great kale and lettuce. But a white/cream colored gunk is coating everything in the system, hoses, manifold, pump, etc. It finally coated the pump rotor to the point of seizing the pump. The gunk washes off the pump filter, but it bonds to the rotor and plastics, requiring scrapping to remove. Any ideas what this is and how to prevent?

[clairk]

If I was running that system here in sunny Tucson AZ, it would be hard water deposits.