Here are some observations on root growth with my cephalotus plants.
This is one example of how I grew cephalotus in a fish tank.
I guess the best way to explain the set up would be to list everything from the bottom of the tank up to
the plants. At the bottom of the 45 gal (high) fish tank there was 2 inches of water with a stone fish tank bubbler
to keep it aerated. Above that was an air gap of 8 inches which had overturned pots. Above this was egg crate material that sat
on the pots. I had a layer of fine window screening on the egg crate material. I then placed a 3/4 inch nylon rope across the egg crate material from one end of the tank to the other. On the ends I had the rope go threw the egg crating all the way to the bottom
of the tank. This was for wicking the water up to the media. Then I added 8 inches of soil and my plants on top.
I did cover the tank, and only used a two bulb T-12 shop light for lighting.
The cephalotus plants I added grew very well for a couple years, hardly ever having to water them.
The problem I found growing the plants this way was that the roots grew threw 8 inches of soil,
threw the fine window screen and then hung down all the way to the water at the bottom of the tank.
It was virtually impossible to remove a plant from the tank without damaging the fine roots.
Using the rope to wick up water into the media was ok, but the soil was always just barely damp.
The plants seemed to seek out the water source and grew roots 16+ inches long.
If I hadn't grown them myself, I would have never believed that they could grow such long roots.
The fact that I could only add plants to the tank and not remove them for fear of severe root
damage, and the fact that the set up was just too big to move around I shut down the whole thing.
I still grow cephs in tanks, just smaller, putting 8 inches of media right on the tank bottom.
It's a much easier way to go and if the tank is covered they will only need watering once every couple months.
I have plants that grow stolons just under the soil surface right across the tank.
Some stolons being almost a foot long. You can remove the plants much easier, with less stress on the roots.
Cephalotus plants can, and do grow very long tap roots, but I'm not so sure if it's necessary
for good growth. I've had beautiful plants in a 3 inch pot, and single plants that were the size of a dinner plate.
To me cephs can be a real pain in the rear, but you gotta love em!
Just some thoughts.