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Have you germinated cactus seed before? Its the same for Monkey Tail Cactus (Cleistocactus colademononis). I use cactus soil (my favorite is Miracle Grow but there are many) with the big pieces taken out in 6-cell pacs. I save the deli food containers that have plastic bottoms and clear tops (with holes cut for ventilation) and make little greenhouses. A heat mat is a must.
The top thin layer of soil is really fine cactus potting mix (put it thru' the colander). Make sure the soil is moist enough to absorb moisture. Sow the seed on top of the soil - don't bury them. Water from the bottom to get the soil wet (no standing water!). The soil needs to stay constantly damp but not soggy. The idea is to create a humid, warm, damp environment - perfect for mold and cactus seeds. If the soil surface dries, mist it with a very fine mist. Keep the fungicide handy (I use a liquid spray - cinnamon is too big). As the soil dries, moisten it with a spray bottle. Once in a while, you will have to add water to the tray.
Keep it in an area with no direct sun (mine are in north facing windows) and take the lid off for awhile if the plastic top mists over.
Cactus seeds germinate when they are ready to.
A few days or a few weeks. I've re-used cactus starting soil years later and had baby cacti pop up in the new pot.
Let us know how you do.
Daisy