That is a good idea on the dirt. Don't do it in that jar or any jar where the neck is smaller than the jar. It will be a pain to remove.

Do not add any dirt. Never use native soil...unless of course, you are planting in-ground. Those roots are plenty developed to place it in a pot with commercial potting mix (not moisture control type). You are a long way off from thinking about pruning.

Two days planted...so far so good!!! Thanks for the advise.

Nice! Just be careful with the over-watering from here on. That soil looks like it holds plenty...which is great for the transition from full water, but I see you had a lot more roots already developed in that jar.

Which way does that window face? Any chance of sunburn?

I'm betting this thing will just take off in growth in the next few months!

I quit starting my seeds in water years ago. I just take the seed, dip the bottom in a rooting hormone and put it directly into a pot of cactus soil then water. I leave about 1/4th of the seed out of the soil. In a couple of weeks, maybe a month, the seed with split and a sprout will emerge. They grow twice as fast planted this way. Let the top 1/4" of soil dry between watering. One leaves emerge, fertilize at half strength weekly and move to a bigger pot as needed. Always keep the very top of the seed above the soil line so it doesn't get rot.