First, welcome to Tropical Fish Keeping forum. Nice to have you with us.
I've never tried these Aponogeton "tubers" (to use the correct term
), but I believe a couple of other members have posted about them previously, so if they see this they will assuredly chime in. My comments will be general.
With one exception, all of the cultivated aquarium species of Aponogeton have a tuber or rhizome, which they use to store nutrients. Most species need a rest period during which they will lose their leaves; in some species the tubers should be removed from the aquarium and kept in a more dry than wet condition, while in other species the tuber may be left in the aquarium. This is based on the natural habitat conditions of the various species. The nutrients in the tuber allows the plants to sprout again. Aponogeton rigidifolius is the only cultivated species that does not have a tuber, though it has a long thin rhizome.
I have a couple of Aponogeton species, those in our profiles in fact, and I just leave them alone when the leaves rot off, and after a couple of months they sprout new leaves. Our fish and plant profiles are under the second tab from the left in the blue bar across the top of the page. You will find most of the commonly seen fish, and some not so often seen species, with data on water parameters, numbers, feeding, etc. The plants section has quite a few species now. If the scientific or common name in the profile is used the same in posts, it will shade and you can click on it to see that profile, for example Aponogeton crispus and Aponogeton undulatus.