Stalled cycle?

aspxct · Sep 21, 2026

Hey guys, I am cycling a 252L Fluval Shaker. I started the cycle with 4oz of Fritz Turbostart 700 on 14th September and I added 200 drops of Dr Tim's Ammonium for a fishless cycle. My tank is quite heavily planted too. The filter I am using is FX2 and I added 1kg of Matrix + Purigen to it too. The water was cloudy for about 1 week and finally cleared up almost entirely yesterday, I'd say it's about 95% clear now. After testing the water daily, I have noticed my ammonia and nitrite has not budged from 1-2ppm and 0.25-0.5ppm since the start. My nitrate was sitting at around 40-80ppm and has been sitting at around 20ppm for about 3-4 days now. I even squeezed my 22L filter into my FX2 filter last Friday (18th) and still no changes. The plants are growing amazingly well too. So my question is, is my cycle stalled or has there just not been enough time? The only reason I am asking is because I would've expected at least SOME reduction in either ammonia or nitrite now but it doesn't seem to have moved, at least the colours on the API master test kit look very similar which doesn't really help either...

For reference, I used AquaCare Bio Boost for my first 22L tank which fully cycled in 1 week so not sure if my expectations are high because of a lucky first cycle or not.

gimme30 · Sep 23, 2026

It's probably not stalled, just needs more time. At the cellular level under ideal conditions certain bacteria can double in 30 minutes, but it takes longer to establish a colony over the complete ecosystem. I'd give it a couple more weeks at least and see where you're at then.

Essjay · Sep 23, 2026

It takes longer than 30 minutes for these bacteria to double. And nitrite eaters multiply slower than ammonia eaters which is why it can take longer to clear nitrite than ammonia.
TwoTankAmin is our cycling expert, this is a quote from one of his posts

TwoTankAmin said:
Under optimal conditions the ammonia bacteria can double in about 8 hours. Slower are times closer to 10 are more likely in tanks

gimme30 · Sep 23, 2026

Essjay said:
It takes longer than 30 minutes for these bacteria to double

For the only bacteria ever mentioned in forums like this-nitrobacter/nitrosomanas. There are many more present in our water but the point was that while certain bacteria can reproduce that quickly you're not going to see a tank cycled in a day.

Jennet · Sep 23, 2026

I started with my 80 litre tank in early June, just gravel and some plants. I put in some fish food and started to read on here as my knowledge was well out of date. I had aquariums in the 70's and again in the 80's. I added some ammonia in July after reading about cycling and followed the instructions given on here in the cycling thread. I have only recently added 8 tiny chilli rasboras and 4 celestial pearl danio's.

Alongside of this in late July I started a small 24 litre tank from Vets 4 Pets and added some of the water from the bigger tank, along with a filter that I had taken the sponge from and I had just dropped into the bigger tank and left there.

It takes a while to get enough good bacteria built up to be able to put more than the one or two fish in to get a cycle going like we used to do in the 70's.

Long and slow may not be what you want to hear right now, however it is the best was to go. So as the others have said, try to hold patience and go with the flow as it were.

Now comes another important part. Have you any idea of what fish you wish to put into your aquarium yet? What are your starting water parameters, as this will normally guide you towards the fish best suited to your natural water from the tap. GH and KH are important to be aware of, especially at the start.