Fern Food?

what should I use to feed/fertilize a fern? any good soil recommendations would be appreciated as well....{Boston Fern}

All I ever used was Jack's Classic 20-20-20.

I made my own peat based mix and added pine bark nuggets, no lime. Ferns like it on the acidic side.

Used to have a small rare fern/orchid nursery.

Wet