Nitrite is produced in the aquarium by the biological filter.

Standard test kits measure total ammonia (ammonia plus ammonium)without distinguishing between the two forms. The following chartgives the maximum long-term level of nitrate-N in mg/L that can beconsidered safe at a given temperature and pH. Again, note that a tankwith an established biological filter will have no detectable ammonia;this chart is provided only for emergency purposes. If your levelsapproach or exceed the levels shown, take emergency action IMMEDIATELY.Should ammonia levels become high during the cycling process,corrective measures will need to be taken to prevent fish deaths. XXXdescribes such procedures in detail. Most likely, you will simplyperform a sequence of partial water changes, thereby diluting ammoniato safer concentrations.

What would cause high levels of nitrite if there are no fish in my tank yet

Of course, such large changes are not generally possible with a marine tank, though they work very well. This is why saltwater hobbyists often rely on nitrate-reducing systems like live rock and deep sand beds, and it is why reef aquarists usually keep only a few small fish that are lightly fed to minimize waste production.

Do a 30% water change as soon as possible

We have had a new 48L tank running, with no fish in it for three weeks and have high nitrite levels Every couple of days, do a 10%-15% , and after about a week,take a sample of your water to a fish store to get it tested. Most will test fresh water for a minimalfee, or even for free! If the store you got the fish from won't, checkto see if there is another local store that will. At this point, yourwater should test with high ammonia and maybe a trace of nitrite. Ifit isn't, don't worry. Just give the tank time. The cyclingprocess usually takes six to eight weeks.

How to remove nitrate from the aquarium | Algone

Fish waste and decaying fish food release ammonia into the water, and ammonia is severely toxic to fish. In a new fish tank, the ammonia quickly builds to dangerous levels, but is non-existent in established tanks. This is because bacteria from the genus Nitrosomonas or Nitrosococcus will grow and inhabit any environment with high ammonia levels, and they eat ammonia and remove it from the water. An ammonia-containing tank will develop a culture of ammonia-eating bacteria after a few weeks. This isn’t the end of the cycle, however. The ammonia-eating bacteria remove ammonia but convert it to nitrites, which are also toxic to fish.

Nitrites and the aquarium nitrogen cycle | Algone