is the end result of the nitrogen cycle and is harmful to fish at 80+ ppm
. It's more harmful to mobile inverts at 40+ ppm
and harmful to corals/sea stars at 20+ ppm
. Reducing the no3
level to 20 ppm
or less within the next week or two is critical for the tanks health.
test kits only test up to 80 ppm
and if you are still showing 80 ppm
after the 40% and 20% pwc
then it was considerable higher then 80 ppm
to begin with.
Need more info:
Size of tank?
How many fish and their sizes?
How much base/lr
is in the tank (lbs)
Is this a reef tank with corals or fo
Is there a clean up crew? (snails, hermits, shrimp, ect...)
Is there a sump and if so how large.
Doing large pwc
(50%) with no3
free water is the only way to reduce no3
I don't like doing large pwc
on tanks with inverts/coral/sea stars due to the risk of osmotic shock due to possible large swings in ph/sg
/temp. If your tank does have any inverts/coral/sea stars then I'd recommend doing no more then 30% pwc
every other day until no3
is reduced to 20 ppm
or less. The other option is to remove them to a clean plastic
bucket and drip acclimate them for a couple of hours to the tanks new parameters. (don't expose sea stars/corals to air)
If the tank is fo
without inverts you could do pwc
as large as 70% but it's still risky unless you have a refractometer to very accurately measure sg
levels in the pwc
water to match the tank.
Either way you still want to mix your pwc
for 24+ hours with a strong ph or pump and match the sg
/ph/temp as closely as possible to the main tank.