Choosing a hydro medium
Inert
Most hydro media have little carbon, so they do not compost away in one cycle
Organic extras
Peat, chips, and bark slowly react and should be replaced over years
Long life
Perlite and LECA are the usual durable choices
Glass rock
Puffed-glass stones wick, hold water inside, and can be boiled clean for reuse
Moisture tune
About 1 part vermiculite to 10 parts LECA coats pebbles and raises hold
LECA
Make
Clay baked near 2200 F expands into light, semi-porous pebbles
pH
Neutral, so it does not swing the solution by itself
Air
Gaps between pebbles keep oxygen on the roots and cut waterlogging
Systems
Works in reservoir, wick, DWC, NFT, aeroponics, ebb and flow, and drip
Rinse
Wash until rinse water tests near pH 7 before the first fill
Rockwool setup
Air reserve
About 18 percent of the block stays air even at saturation
Easy drink
Water tension does not climb as the block dries, so roots can use almost all of it
New blocks
Soak 24 hours in water near pH 5.1 to dissolve leftover lime, then flush with nutrient solution
Ongoing
Keep solution no higher than about pH 6.1 to offset a slight leftover alkalinity
Sizes
Starter cubes for cuts and seedlings. Four-inch cubes for small plants. Slabs under cubes for larger ones
Rockwool handling and reuse
Plastic
Leave slab wrap on the top and sides. Open the bottom for drain. Cut an X to set a cube on a slab
Dust
Wet it first. Wear a mask, long sleeves, and gloves. Loose wool is harsher on lungs and skin
Reuse
Pull or cut old roots, soak 24 hours in 3 percent hydrogen peroxide, then rinse well
Disposal
It does not break down in soil. Reuse is the cleaner option
Loose wool
Absorbent or repellent grades let you tune pots, with the same fiber precautions