I didn't know how to explain it any better in title...
I'm using the masterblend 12g, cal nitrate 12g, mag sulfate 6g hydroponic solution, see here
After it sits in my Kratky hydro tub a few days it gets a film on the top of the water.
A few more weeks and the film solidifies and when touched breaks into small pieces.
The water I used was from a dehumidifier, raised pH with 1 tsp of baking soda to about 5.5 then added nutes.
All of the nutes were pre-dissolved in a high concentrate 1 gallon jug prior to adding to the tote.
1. Is the crusty stuff harmful to plants? (lettuce seems to be doing OK at the moment)
2. How would I prevent the crust in the future?
I'm planning a self-leveling/watering system that has 1/4" hose fed by a small float valve and reservoir; but I'm afraid it would get clogged.