My experience so far, tried 3 times to grow it:
First attempt from TC went very bad, but I'm sure that the cup was already old/bad stored.
Second attempt from TC, I splitted the cup in 4 pieces, 2 planted straight in the soil and the other 2 let them float for 2/3 days. I've lost 2 pieces (1 floated 1 in the soil), the 2 that survived thrived but the floated ones gave me better roots.
I tried a third time because my light broke and I've lost around 300€ of plants.
Bought directly from an hobbyist, he gave me around 6cm piece planted straight in soil. This single piece now has 3 head (it was 4, but I cut one off because it turned in Araguaia, sometime happens you have to cut it off), it has veeeeeery long roots, and it's very slow but consistent. Is very hardy when properly adapted to water conditions.
My chemistry is:
GH 5.2
KH 0
pH 5.1 during injection, 200+ par at substrate