you need biger pot

echinopsis sp

perhaps you took seed too soon always wait for the fruit cracks open then take seed

H2O2 is harmless for seedlings I use 3%

Euphorbia ledienii

I do not sterilize the seed or substrate .when I put substrate in the pot i put water in which was dissolved fungicide .I pour the water until it starts to leak from
drainage holes then I put seeds and put some more water and put all in bag . Sometimes moss appear then I sprinkle H2O2

my soil is usually dry after one day in summer how long Ilet it dry depends of cactus

in my opinion is better than perlite and I use it for cacti and I have no problem with water retention in the substrate

vermiculite is good

I think the woman with the first shot even wrote a book :hh

snails probably eat your cactuses

they are spread from plant to plant sparge all, including shelves and pots

did you water it enough ?

Is it possible to cross this two cactus ? sulcorebutia rauschii & rebutia

#2 is not sedum it is mesemb