Rosie,
Since you are only trying to revive your Phal with water culture, it should work just fine. Phalaenopsis only starts to have problems with long-term water culture. I had a pulcherrima keiki that I attempted to root in water culture. It rooted, but I kept it in the water and water started seeping up into the leaf axils and the top of the plant, leading to rot (luckily I had a second keiki that I was trying a different method with that worked, though I wouldn't recommend it). Phalaenopsis can be grown long-term in water culture with a little extra care taken in regards to water level and sterilization, but do better in other growing mediums.
In your situation, you don't need fertilizer or algae in the water. Some sort of rooting hormone will probably enhance your results, as others have suggested. Just watch the water level and make sure water isn't seeping up into the leaves.
If you want more info on water culture, I recommend checking out threads posted by Sun rm N.E. She has been using water culture for 5 or 6 years now. Some plants are only revived in water culture before moving to SH, a few grow as well or better in water culture.
Mostly the 2nd page:
Onc. Sharry Baby in water culture
Here's an article that Sun rm N.E. referred me to when I first started playing with water culture.
Water Culture
I'm also worried about how well orchids in S/H travel, since about half of my plants travel across the state of Washington 2-3 times a year. Though I guess it wouldn't be any worse than CHC or bark. 
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