Short answer: not needed.

I used to use fish emulsion on ferns. Nice and stinky when diluting but no odor after use.

I've used Miracle Grow the past 10 years (weak and weekly as the saying goes). Can't say I've noticed any difference.

iris gal: Did you use the regular MG (green box) or the one for acid plants (blue box)?

Jean: Last year I saw a great improvement when I occasionally fertilized them. I think potted plants get 'vitamin deficient' if not fertilized.

Westelle, I use the regular (Costco's big box).

And you are right about potted plants getting depleted. Nitrogen runs right thru every time they're watered. You also might refresh their planting mix. Not sure how often. I just did an asparagus fern (the upright bushy foxtail type) that had been unattended ~ maybe 8 years. Both divisions looking great. Of course some ferns can't be divided but you can shake loose some of their potting mix and add fresh.