wilson23
Anytime you have measurable nitrite - you know you had ammonia.
You mixed up your saltwater and added the live rock and live sand.
Chances are very good that the rock and sand had "some" bacteria present.
How much - no telling.
Enough to consume and convert any ammonia from die off to nitrite ......... and enough to convert any nitrite to nitrate.
Whatever shape the bacteria colony was in at the time of your test readings ........ they were what they were.
In other words - you tested the water and everything looked fine.
It looked fine for keeping live rock and sand. That's all you had in the tank at the time. It was balanced.
Then you added 2 fish.
Fed the tank and fish began to produce some additional wastes that the tank ( bacteria ) were not used to seeing.
Whenever we add fish or feed a new tank - there is an upset.
The bacteria now have additional food souces, and will respond to this the way they do. They'll reproduce and populate even more surface areas of the tank, rock, sand and all other solid structures in the tank. If you've ever felt that slimey goo that covers filters, insides of hoses/pipes and any other solid surfaces of an established marine tank - you're feeling the bacterial slime.
It's a good thing.
Bacteria colonies, their actual numbers, are limited by the available food and nutrients they need.
The nitrogen cycle is on going and beneficial aerobic bacteria respond to the levels of food and oxygen.
At this point I would not add anything to the tankwater at all in the form of additives.
I would just wait and I'm sure your nitrite will drop back down to zero.
Keep an eye on your pair of percs though - and if they seem stressed - then remove to another tank until your numbers are right.
That's my thoughts
