for my tank, i don't check no3, waste of time
and money.and no worries.....just change 10%
of water every fortnight..feed with dried brine
shrime, once a day....and my clown is growing
big.....happy with a brown tang....................
and mandarin.......but of course water is matured
and must maintain filteration system.
i let my system to run in for 2 mnths before
introduce fish....