Yes carbon is not needed. Its purpose is to remove smell or meds in a tank and also to a minor point it can clear water for a short amount of time. Many suspect it has something to do with hith.
Great looking discus! But if you’re not seeing them eating that could be a problem. Assassin snails can also be nuisance snails and over populate a tank. They are also the laziest snails. All they do is eat other snails they don’t eat algae or any thing else.
Al I don’t know I’m no pro. But my swords always grew great and had huge roots. Even in pots. There I would have root balls that pushed the gravel out of the pots over time. I do feed ferts now but nothing like I use to in planted tanks. All swords got tabs when the growth would slow down. I’ve been having a very hard time growing swords lately. Again just not putting enough time into the plants I have. Too much time with discus! Also with the shops all selling emersed plants it’s harder to get these sword growing correct. I recently got 4 very small swords I’ve planted in pots with aquasoil on the bottom(using like root tabs) and these so far are looking good.