Homer said:I couldn't really say why the fern is dying from the description. What type of substrate are you using? have you checked the roots? What type of fern is it? What type of lighting are you using, and how far from that lighting source is the fern?
Okay, enough of 20 questions.
As for ferns I am successfully keeping, I have the resurrection fern (Polyploides sp.), some type of Maidenhair fern (Adiantium sp.), a lemon button fern (Nephrolepis cordata 'duffi'), and some unidentified fern that has started growing spontaneously. All of these ferns grow in very moist parts of my terraria near the water feature, but my substrate is a rather course type of media--1/4 and 1/2" coco husk chips mixed with activated charcoal.
The lemon button fern has sent runners all over the tank and I've given away at least 10 plantlets. The resurrection fern has steadily grown to about 2x its original size in the course of the last year. The maidenhair fern has been in its 10 gallon terrarium for about 4 months and is about 2-3 x its original size. Most of these were bought at Lowes for less than $3 each (the Exotic Angel Brand).
This is my first attempt to post an image here, so I hope it worked! It works differently than the other forum I use with this same format. No image hosting, huh? I guess that keeps bandwidth down.