Fish tank water for orchids?

[mheleo]

I have two large fresh water fish tanks (75 & 150 gallons) and as part of its maintenance I do partial water changes every week. I hate to dump the water which is rich in nitrogen (40 ppm of nitrates) and fish wastes. In the summer time, I use it to water the lawn and my vegetable garden. Just wondering if I can use it to water my orchids. What do you guys think?