One of those books about natural chemical uses states if you add powdered mustard out side the worms will come to the soil
I am not really a fisherman so never tried it myself.
How mush perlite does your pots have?
I have been reading a lot lately about what was used for oil spills zeolite mineral for retaining water in soil
It looks like cat liter you can get it at a feed store for cheaper then other places as pdz (a 25 lb bag for $10)
but your in Romania maybe try similar feed stores over there..
https://www.tractorsupply.com/tsc/product/sweet-pdz-stall-refresher-25-lb-5065990Also Over here We have a new Invasive Worm that eats compost degrading soil called jumping worms
I quote this from the MN Department of natural resources
"The Minnesota Department of Natural Resources is cautioning gardeners and anglers to be on the lookout for invasive jumping worms. These destructive worms can quickly degrade soils and damage garden plants and lawns.
“Jumping worms are a relatively new invasive species in Minnesota and they are a threat to gardens and forests,” said Laura Van Riper, DNR terrestrial invasive species coordinator. “They make rich soil more like coffee grounds. They eat plant roots, damaging garden plants and sod.”
Jumping worms are a type of earthworm that looks similar to other common earthworms such as nightcrawlers. They are called “jumping worms” because they wiggle intensely when disturbed and sometimes appear to be jumping. Native to Asia, jumping worms have been confirmed in limited areas of Minnesota since 2006, mainly in the Twin Cities and western suburbs and in Rochester. It’s believe that they were spread throughout North America by people moving potted plants, soil, compost, mulch and fishing bait."