The best replacement for hydroton is perlite.

The best alternatives to hydroton are rated as following:
★★★★★  perlite
★★★★  coco
★★★★  rockwool
★★★  gravel
★★  lava rocks
★★  hydrocorn
★★  growstones
★  hydrostone
★  leca
★  rocks
★  expanded shale
★  coco coir
  higromite
  false bottom
  lava rock
  coir
  sure grow
  grodan

Your alternative for hydroton is not listed? Suggest!
Speaking about hydroton, one probably shouldn't forget about rockwool.

Other search terms related to hydroton and their ratings are:
★★★★★ rockwool
★★ ebb and flow
★ drip system
You have in mind a companion for hydroton and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of hydroton in all years. Click on graph for more.
hydroton
perlite
coco