Hello! Also, can a tank be cycled with 0 nitrates?

MayEyeElegize

So nice to join this forum! I'm sure parts of my question have been answered before, but I wanted some input on how my current tank is cycling. I'm not new to fish-keeping, but I've started this tank from scratch after moving and I'm confused about some things.

My new tank is 10 gallons, and I've had it for 8 weeks now. I dosed with fish food, ran my HOB filter, and watched my lovely plants grow. I was doing 50% water changes once a week (with prime.) The substrate is Fluval Stratum, which has been lowering my pH to about a ~6.8. Temp is 75. I tested infrequently at first, and my ammonia was always 0.25 ppm with 0 nitrites and 0 nitrates. I figured it was just going to be a longer cycle, so I waited some more.

The algae is thriving, the plants are doing well, and I've spotted some pond snails and a couple of detritus worms while I was moving some rocks. For all it SEEMS like the tank is established, I now consistently have 0 ammonia, 0 nitrites, and 0 nitrates. I've been making the water fairly gross with all the fish food I'm putting in recently, but it's just not changing these levels at all.

I have some ideas about what I'm doing wrong, but I wanted some outside input about why things are working the way they are.

1. Can plants absorb so much ammonia that the cycle will never start?
2. Can plants absorb so much nitrate that they hide the fact a tank is cycled?
3. Should I be dosing straight ammonia or adding live bacteria to try to get a serious cycle going?
4. How long do I wait to add a living creature if nothing seems to change?

I think I'm probably making some rookie mistake, but the last tank I cycled did so very quickly and easily. If I had been testing this one super consistently for the first couple weeks, maybe I would have picked up on an ammonia/nitrite/nitrate spike, but I'm not 100% sure those ever happened. I've never had a cycled tank at 0 nitrates before, so I assume this one is not cycled.

I very much do not want to risk fishy lives, but I'm not sure what my next step should be.


RamshornHitchiker.jpeg (Dirty tank corner with ramshorn hitchhiker.)

Thank you!
 

bcsay720

Hello! Welcome to FishLore.

I never believed people who said their cycled tanks ran at 0 nitrates. But as someone who has a 6 month old tank (much of the plants and media are almost a year old) that used to run at 10 ppm that now runs at 0 ppm, it's possible. If you have plants that really suck up nitrates, like floaters, hornwort or certain semi-aquatic plants like pothos, then you are likely to run at 0. I fertilize twice a week, and I still never see a single nitrate. I hope this helps.
 

StarGirl

Hello Welcome to Fishlore! :)

Was your filter new when you started this tank?

You could get some regular ammonia and dose it up to 2ppm and see if it drops to zero overnight. If it does you are most likely cycled.
 

ValkyrieLips

Technically yes, but I think it's more likely that an established tank runs at 0 nitrates since the nitrate eating bacteria are difficult to grow if they ever grow at all. I have 1.5 year old 5 gallon tank with 1 betta and only recently did it started testing 0 nitrates where before it was always 5 ppm.
 

MayEyeElegize

Hello Welcome to Fishlore! :)

Was your filter new when you started this tank?

You could get some regular ammonia and dose it up to 2ppm and see if it drops to zero overnight. If it does you are most likely cycled.
Thanks!

Yep, my filter was new. Some of my plants were grown submersed and were still wet until I put them in, so hypothetically I could've introduced good bacteria with them (and those snail eggs.) I kind of doubt such a small surface area could've done much?

I'll get some ammonia and try a dose!
Hello! Welcome to FishLore.

I never believed people who said their cycled tanks ran at 0 nitrates. But as someone who has a 6 month old tank (much of the plants and media are almost a year old) that used to run at 10 ppm that now runs at 0 ppm, it's possible. If you have plants that really suck up nitrates, like floaters, hornwort or certain semi-aquatic plants like pothos, then you are likely to run at 0. I fertilize twice a week, and I still never see a single nitrate. I hope this helps.
This is very interesting -- I do have a LOT of dwarf water lettuce in there as well as a small cutting of pothos. I never had a tank with either of those two plants until now...

If I add some ammonia and it cycles without any more spikes, I might have my answer!
 

GlennO

After 8 weeks it’s likely to be cycled but you may not have been adding enough fish food given that ammonia never exceeded 0.25ppm. The resultant nitrate levels would also be very low and quickly absorbed by the plants which would be why they are undetectable. The 50% water changes would also be removing them. No need for water changes when fishless cycling, particularly when levels are so low.

In summary, it’s probably safe to add fish but your BB colony will be tiny so you need to add them VERY slowly and continue regular testing.

Alternatively you can add pure ammonia to increase the size of your BB colony. By doing that you will effectively create a mini cycle that may take several more weeks to complete but by doing that you will have a larger more robust BB colony that can support more fish when the cycle is finished.
 

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