Backyard Aquaponics
A place to discuss aquaponics

As TCLynx pointed out, it is best to keep the nitrates in a range you can read them. I have the same problem she has, namely high nitrates to the point of not really being able to read them. Anything higher than ~40ppm is really hard to distinguish. Is it 80? 160? I've no clue, really. (Does it really matter? Perhaps not. Especially for the plants!)

Say I really wanted to measure it, though. What if I dilute down the fish tank water with rain water (assuming that rain water is ~zero nitrates) five to one or ten to one and then use the same test? Wouldn't 40ppm on that really be 200ppm (5:1) or 400ppm (10:1)?

The vials are 1tsp (5ml). I was thinking of a 1ml syringe. (pretty cheap, ~0.13US$ea HERE, probably cheaper (because of shipping) at your local pharmacy)

Thoughts? Errors? Bring another grow bed online?

definately.

standard practice for many chemicals is to water them down to a point where you can read them on the scale you have. certainly wont be much further out than average error for a backyard test, anyway.

a syringe is also an excellent way to measure stuff out. I always prefered to take water from the tank with a syringe too, rather than dip the kits little test vial in every time.

Definitely bring more growbeds online, or perhaps make a floating raft for the top of your fish tank with some fast growing water loving plants in it..