Cycling help, please

[NigelK8485]

It's been 8 days since I dosed my 150 gallon with pure ammonium chloride, getting it to 4 ppm. I also added a little piece of a sponge from a 5.5 gallon established tank figuring it couldn't hurt.

Today is the first day I noticed any decrease in ammonia level, it went down to about 2-3 ppm. I decided to go ahead and test nitrites and nitrates, nitrites are at 3-5 ppm, nitrates between 5-10 ppm.

My question is is it normal for nitrites and nitrates to be showing up already when the ammonia hasn't even decreased to 0 yet? Especially the nitrates.


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[Coyne]

There are two types of bacteria that you're trying to cultivate. I don't know their names, nor do I feel like looking it up, so I'll just call them Type A and Type B for now.
Type A converts ammonia into nitrite.
Type B converts nitrite into nitrate.

Normally in an freshly cycling aquarium, Type A grows first followed by Type B. So you have nitrite hanging around for a bit until you have enough Type B to convert it into nitrate.
Since you're using an established filter sponge to seed the new tank, you introduced both types at the same time. This means that as soon as the ammonia is converted into nitrite, you already have the Type B bacteria present to instantly begin converting it into nitrate.

 

[PNWaquarist]

Sounds like you're on schedule. I'd wait until the ammonia is down to ~0.5 ppm and then dose back up to 2 ppm ammonia. You don't want your nitrites going way above 5 ppm, as some say that this stalls the growth of the nitrite-oxidizing bacteria.


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