I thought that might be true, but I was unsure because it was poking up so far from the substrate. I put root tabs in a while ago, but subsequently vacuumed up the remains, because I ended up with an algae bloom and I thought I might be providing more nutrients than necessary. Am I being paranoid or could the root tabs have been the cause of the algae bloom?
If you disturb the root tab and allow it to enter the water column, yes it could/can cause issues.
If you are dosing the water column, I would for go adding root tabs then. Root tabs can help, but are unnecessary.
There is plenty of research out there that has proven that you can completely remove the root system on swords and their growth was unaffected as long as they had a source of nutrients in the water.
(Cedergreen and Madsen 2001)
There is a lot of mis information about root tabs flying around. A sword does not 'need' root tabs to grow. Can swords get nutrients from it's root system? Yes. Can swords get nutrients from the water column? Yes. By measuring their mass increase and using both methods separately, the sword had a larger mass when feed with just water column nutrients then with only root nutrients.
The highest amount of mass was produced when the plant had both root and water column nutrients.
(Barr, 2006)
It is 'best' to provide both, but they are not 'needed' as some people claim.
I have grown many different types of swords without adding anything to my sand substrate.
EDIT: With the large size substrate that you have, I wouldn't add any more root tabs. All the nutrients in the root tab will just enter the water column anyways.
And the more I read into it, it appears that most aquariums will just leach their root tab nutrients into the water column.
(Carignan and Kalff, 1982; Fisher and Reddy, 2001, Malecki et al, 2004)