Personally, I have found twisted val (valisneria spiralis) to be difficult to grow. When ever I try it, it melts.
However most other types of val (americana, rubra etc) are very easy to keep. Just use a good liquid fertizer and trim like grass as they grow.
as for the onion bulb, you can also trim this one like grass too, but this one will benefit from a root tab added near the bulb roots every 2 weeks.
both are very easy to grow.