Hello, Dorothee,
I have the following plants in my tanks: java fern (Microsorum), fountain moss (Fontinalis), water sprite (Ceratopteris thalictroides) and “Süsswassertang” (Lomariopsis, they seem to also use the German word in English). Swimming plants are Salvinia natans, Riccia fluitans and Limnobium.
Limnobium doesn’t like a cover, that’s right. As far as I know many swimming plants do not like to get wet from above – e.g. by condensation.
With Ceratopteris it’s as you’ve been told before in this thread – be patient. It “dies” at first in acidic water – but if you have some “hard pieces of leaves” left, just let them float. They make adventive plants after a while – and these survive!
What’s a real success – and nearly not mentioned in context with acidic water – is Lomariopsis. It proliferates even in water with a pH of around 4,5, looks beautiful and provides wonderful hiding places for young fry….
In the middle java fern and some fountain moss, below and on the right is Lomariopsis, and above on the right it’s Riccia:
Lomariopsis again: