This thread is about arowana.
Arowanas do not like high nitrates !
It's true a lot of of fish can tolerate 40ppm nitrates.
I suggest you go ahead and use water that has 40ppm as change water, and see what level of nitrates you have when it comes to next water change !!! I bet for the life of me that with an arowana which already has nitrates in the tank, and the change water has 40ppm of nitrates, that the nitrate level on the next water change will be greater than 40ppm nitrates !!!
