nitrate readings

Here are my specs: 55 Gallon Freshwater Tank Heavily Planted Marineland Penguin 350 Filter 2 Airstones 25 Mollies 78 Degrees Ph 7 Ammonia 0 Nitrite 0 Nitrate 180+ In 3 months I’ve not been able to get my nitrates under control. I’ve been doing 20-30% water changes weekly using distilled water...

I am a woman who can detect color! So why do I have such a problem seeing the difference between 10 and 20 nitrates on the liquid API nitrate test? I know men are often known to be a bit color blind, especially witb blues and greens and reds, oranges and yellows, so I don't see how in the...