Tank Cycle Stalled

The friendliest place on the web for anyone with an interest in aquariums or fish keeping!
If you have answers, please help by responding to the unanswered posts.

GraceTheNoob

Aquarium Advice Apprentice
Joined
Sep 14, 2021
Messages
13
Please help!! I don't know what I'm doing wrong.

I'm doing a fishless cycle. I've been going for around around 3 weeks now. The tank is fully set up, filter and bubble stone running, loads of gravel, plants, biological media within the filter etc etc etc.
The cycle seems to have stopped halfway through.

Every time I dose with ammonia to 2ppm, the ammonia levels fall to 0 within 24hrs. This has been the case for around 2 weeks. Good stuff.
But my NITRITES just don't seem to be going anywhere. The only time my Nitrites fall is when I do a water change. And then it's right back up when I dose the tank with ammonia again (NB I don't dose every day because the nitrite level absolutely rocketed out of control).

What's baffling me is that tests for nitrAtes are coming up positive as well. So clearly the Nitrites are being converted into Nitrates, but the overall level of Nitrites never seems to fall by itself? I don't know what I'm doing wrong here. I've used API Quick Start live bacteria, and yesterday added Dr Tim's One and Only.
I use API 5-in-1 tests to read Nitrites and Nitrates, and a separate API ammonia test to read the ammonia.
Can anybody help?
 
Nothing unusual here. Fishless cycle typically takes 6 to 8 weeks. You are only starting. The ammonia to nitrite side of things is normally much quicker to progress than nitrite to nitrate.

What you have to remember is you keep adding ammonia, and this is going to nitrite. If you keep adding ammonia nitrite will rise if it doesnt go to nitrate. You arent seeing nitrite rising, so some will be going to nitrate. And this is what you are seeing.

Also, 1ppm ammonia goes to 2.7ppm nitrite and then 3.6ppm nitrate. So it doesnt take much ammonia to produce more nitrite and then even more nitrate. So small drops in ammonia and nitrite that might not be detectable in your testing (testing isnt all that accurate) produces enough nitrate that is detectable.
 
Thank you for your response!

Do you know how long I can go in between dosing my tank with ammonia? I'm doing it every other day atm but I reckon it could probably last longer. I just don't know how much longer haha. I just don't want the ammonia-eating bacteria colony to die off and have to start this whole thing all over again!

Thank you!
 
Lets do an example of where i think you are. Might be easier to understand.

You are dosing 2ppm ammonia and that is 100% being converted to nitrite within 24 hours. So 2ppm ammonia becomes 5.4ppm nitrite.

Your nitrite consuming bacteria isnt as well developed, so lets say 50% is being consumed in 24 hours. So of the 5.4ppm nitrite your ammonia produces 2.7ppm of it goes to nitrate and becomes 3.6ppm nitrate. Every time you add 2ppm ammonia, your nitrite goes up by 2.7ppm and nitrate goes up by 3.6ppm.

As your cycle improves more of the nitrite will be processed into nitrate. Eventually the amount of nitrite your cycle can consume will exceed the amount produced by the ammonia and nitrite will start to drop. It will eventually drop to 0ppm and then you will be able to dose 2ppm daily and see nothing but nitrate rising after 24 hours. You are cycled.

As to how often to redose ammonia, the process is to redose ammonia back up to 2ppm if after 24 hours it has dropped below 1ppm. In your case that's daily. In reality missing a day wont hurt anything and will give your cycle a chance to process nitrite without ammonia just topping it up again. Ammonia consuming bacteria will live weeks if its kept wet and oxygenated. A few days wont kill off anything significant.
 
Last edited:
Thank you so much for your help!

One more question, I've heard conflicting information about concentrations of chemicals stalling the cycle I.e. if Nitrite levels exceed 5ppm then the cycle will stall, some people make this measurement out to be the end of the world but its never been explained why.
Is this true? I've been diligently changing the water every time I've got a reading higher than 5ppm of Nitrites (conditioning and dechlorinating the new water of course) with the understanding that the bacteria lives in the substrate and in the filter etc rather than in the water itself.

Have I just been doing water changes unnecessarily?
 
I dont think anyone can definitively say what levels (if any) will kill off the cycle. There are varied opinions, and i think thats all it is, opinion.

People will see a successful (or unsuccessful) cycle process and put it down to something they did immediately before their cycle established (or crashed), whereas cycling is a lengthy process involving exponential growth. Everything happens at the end in one big rush.

For example, "That thing you did the week before your cycle established? May not have anything to do with your success. Your tank didnt cycle in a week because you added something, it needed that 6 weeks of nothing observable happening to give you a base for that last 2 weeks of sudden improvement. Thats how exponential growth works" Thats a general statement not aimed at anyone in particular.

Ive heard that ammonia over 6ppm and nitrite over 10ppm (or other similar numbers) can kill off a cycle. Ive never seen any actual evidence of that beyond anecdotal that may not be relevant, and ive never seen any reasoning.

My opinion for what its worth. I can see how high ammonia can be harmful, so thats something i can go with. Dont let ammonia get over 4ppm. Nitrite? Ive cycled tanks with nitrite off the reading chart, but i prefer to keep parameters where i can read them so i can see progress in what im doing, so i change water if nitrite gets too high to read. I dont think its necessary, but its just my preference and why tempt fate.
 
Oh. And to add, beneficial bacteria lives on surfaces. Filter media, substrate, glass, decorations. Changing water will remove a small amount of bacteria in the water that hasnt established on a surface, so shouldnt affect your cycle in a sigificant way. Only thing i would add, obviously if you are dosing a bacteria supplement (one + only) dont change the water for a day or so afterwards as you will just be removing what you added before it can establish. I Iike one + only. Dr Tim Hovanec developed tetra safestart and his one + only product is an advancement on that. The claim is that Dr Tim was the first person to identify the specific beneficial bacteria in your aquarium.
 
Back
Top Bottom