Carl, you can grow HC in sand but...it's not easy. On the plus side, planting it is easier in sand. You need to get the plant out of the pot, I presume it's in rockwool? If so split one half of the rockwool away & leave the other half attached. Next cut the rockwool so that you have about 1.5 cm of it still attached below the roots. Then cut vertically into 6-8 strips & then push the rockwool down into the sand. Plant at 1 inch gaps, i've found that if you place it like the number 5 on a dice face it fills in faster & more uniform. HC needs light to carpet & lots of it, the more the better. I am using 3.5W per gallon. It also sucks nutrients & CO2 up for fun so once it starts to grow feed it well. The only other plants I have in the tank are Pogostemon helferi & I don't get algae even though i'm using double dose EI. It gives you some idea of how nutrient hungry this stuff is. Good luck, let me know how you get on.
OK thanks. I don't think the HC cuba will form a very good carpet with sand so I will use a plant substrate. This is what I info about my tank
Light-1.2 WPG
co2-Yes, DIY method
Fert- Yes, will buy some TPN+
Is this enough for the HC cuba to form a carpet.
Also I will add some LED lights (strip) and moonlighting dunno if it will make a difference though?
Carl