White stuff

I found a white substance on the top of my rapid rooters I'll try to get a pic http://m.imgur.com/G0KtxU3

calcium in your water??

maybe dried up nutrient salts?

How do you figure out how much calcium is in the water. I'm using reverse osmosis water

RO has nothing in it.

have you fed any nutes yet?

Mold - take off what you can and then transplant in final container - problem was due to water/humity/ root ball size and air movement - any one of these, look s like they are ready to be transplanted any way ? Easy fix problem - then also would not change any thing in relation to nutrients

So I'm doing a dwc with just water to help grow roots then transfer them over to the nute solution. But it has happened in both the nute solution tote and the water tote with the white crap on it also when I took the plants out of the net cups they're was a slim like substance on the rapid rooter.