I don't bother cutting off dead leaves or flowers, used to but decided why? I don't mind the dying leaf look, they poof away, yeah add stuff to the pond. It has never added a ton of muck to the pond. This year was my first bottom cleaning job, 11 years. I used to net now and then gave up nothing much removed.
I had maybe a inch of muck on the bottom. I only cleaned to remove excessive hornwort snake hiding spots.
Fertilizing , once a year, osmocote for flowers. 1/4 cup under the litter. Grooming maybe every other year or any that grew excessively.
Plant tabs were a pita to put in, so I didn’t.