Swords are heavy root feeders so they need root tabs... Here's what I recommend for people that want sand as their "noticeable" substrate... I tell them to first add a 2"-3" deep x 4"-8" wide of planted substrate like flourite where they intend to add plants, then cover the flourite with the sand so the tank looks like only sand was used, and to add some root tabs in the flourite for heavey root feeding plants like swords, crypts, vals...
Then to add new root tabs every 2-3 months to keep the heavy root feeders supplied with nutrients... The reason for the flourite is it has a high CEC (cation exchange capacity) which means it's able to soak up nutrients and release them back to the plants slowly instead of just adding root tabs under sand alone which in this case once the root tabs are gone there's no available nutrients until you add new root tabs.
Say you go on vacation or something... and it's around the time to replace the root tabs well by adding that layer of flourite means you don't have to worry about the plants starting to die off because the flourite will keep them "fed" by slowly releasing the nutrients it soaked up from the root tabs.