ALL living plants respond to fertilizing. The fertilizer reacts with the fungi-bacteria in the soil and after being broken down to usable components, their roots can absorb them. Pitcher nutrients is for something all together different than for growth. Nepenthes MUST have root nutrients in order for them to live. Just insect prey alone would be the same as a human with leukemia and not being able to assimilate sugars and nutrients in a NORMAL process.
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Fertilizing a nepenthes is the difference between the plants fullest potential or just surviving.
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Plants in the wild is always seen with a multitude of pitchers. That's because the soil they grow in have nutrients just not in the usable form you get in a balancedfertilizer.
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With a balanced fertilizing regime, plants produce pitchers with better color, size and form.
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You just cannot grow these plants and allow their only nutrients to be absorbed through their pitcher walls. That is ridiculous!
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So what fertilizer would you recommend?

The one I like because of its low alt is GrowMore Liquid Seaweed Extract. No odor, nor residue and cannot burn plants using this. Never use Miracle Grow/Miracid. Peter's orchid special is also beneficial.
NEVER feed the pitchers with fertilizers, it was designed for insects, not fishfood, not meat, not tropical fish,
Fertilize through the root system only and flush out with plain water in between.

I use shultz plant food plus, I just mix in one dropper full into a gallon of water, make sure it is mixed in well. Add a cup or two of it into the soil near the base of the plant, I usually do it in the morning, and the next morning flush the extra nutrients out of the soil using water.

RainforestGuy,

Are the Nepenthes plants in the pictures yours? If it is, I'm jealous! I got my first one couple months ago from Lowes, it's healthy and producing large pitcher plants. I'm glad to know now what to feed the root system of this plant. Which store in Hawaii carry the GrowMore Liquid Seaweed Extract?

is copper and zinc toxic to nepenthes?

In Honolulu, go to Fukuda Seed Store on Kalani Street, limited hours.
The nepentehs are from other growers who specialize in SEED-original plants. Those found in garden centers tend to be tissue culured material. An inferior grade of plants. But if that is the only ones you can obtain, then they will do. The thing with seed grown plants is that they have a better chance of making seeds while tc plants not always does well.

Your so lucky to live in Hawaii, I bet your nepenthes grow like weeds! mine are starting to slow down, I need to fertilize them again.

I'm actually in West LA. When I looked it up yesterday, we're actually in the 11a zone. I guess I got lucky. :)

Many nepenthes likes it cooler to grow even more colorful and better development with even longer lasting pitchers!