API. It's impossible to find the tropic Marin n03
I did some hunting around for other NO3 test kits and found another post for the Fauna Marin which do work with the Bot and they even have refill kits like the RedSea which are much cheaper. I bought 3 of these below and will give them a try.
http://cm-distributors.com/product/aquahome-test-no2no3-refill/






