Nitrite In QT

[FishinAround]

How much nitrite for how long can a Carpenters Flasher Wrasse and a Midas Blennie tolerate? I've got a 20g QT tank with the above fish, they have been in the QT tank for about a week. Prior to setting up the QT tank I put a couple pieces of sponge in the main tank for 4-6 weeks in the hopes that these would become bacteria infected and I would avoid a huge cycle in the QT tank. Well it appears it worked to avoid the ammonia cycle but not the nitrite cycle. I never saw any signs of ammonia but my nitrites have started to increase. I checked yesterday and it was around 0.5 so I did about a 50% water change and checked it again today and it was down around 0.3 - 0.4. I know the target for nitrite is 0 so my question is, how long can these fish tolerate nitrite and at what level? I was hoping to keep them in QT for about 4 weeks. Is there a nitrite level I should begin to panic at and think about moving them to the main tank prior to to the 4 weeks? As a side note the fish came from MarineDepotLive and appear to be in wonderful health, eating and swimming around very happy with no signs of disease.

[Amphiprion]

Quite a bit, actually. I would not be too terribly concerned about the presence of some nitrite in QT, since it is almost nontoxic in seawater except in VERY high concentrations. The thing to watch for is ammonia and to make sure that it never registers.

[FishinAround]

OK, I didn't completely believe the ammonia test kit I had so I went out and got another one, and it was as I feared, ammonia is actually between 0.25 and 1 with nitrites around 0.3 - 0.4. I can do a water change but this obviously won't bring the ammonia down to 0. Should I worry or just keep the ammonia as low as possible. What level of ammonia would be deadly. If I have to I can move them to the main tank but don't want to take the chance of an ich outbreak.