White Crusties on roots

If you could post a picture it would help tremendously.

 

Are they healthy plants? ...root hairs?
(I've seen roots do some really cool things that I never would have expected when they get happy!)

 

There are several potential sources of buildup within media, and the water supply is just one.

Additionally, fertilizer, plant waste products, and substances extracted from the potting medium itself can all get deposited at the surface as the water evaporates.

 

Without you telling us more about your feeding regimen, how you prepared the LECA, etc., we cannot say what the stuff might be, let alone how to get did of it.

Also, if you can increase the humidity in the growing area, evaporation wil slow, and any buildup will take much longer to occur.