Can you cycle a small tank (fish-in) in a week?

[bensmithuk]

New to fishkeeping. Have tried to read a lot but confused by what feels contradictory advice… (25L tank)

Summarising online advice: Fish-less cycle is best but if you have to / need to do fish-in then water change whenever you reach these levels: Ammonia 0.5ppm, Nitrate 0.5ppm or Nitrate 20ppm. This could take up to a few months.

My local store: Cycle your new tank fish-in and let Ammonia / Nitrite spike up to 'high' levels. You only need to be concerned / water change if the levels stay high for 4-5 days. This should take a a week or 2 max.

Can anyone help me understand what feels like a huge difference? Some or all of it may be me misunderstanding what I am being told.

[John Linklater]

Your local store should be ashamed of themselves. High levels of ammonia will kill your fish or severely shorten their life if they survive.

If you go to the guides section on this site there’s good info on how to cycle your tank.

Cycling without fish is best. It seems daunting but once you start it becomes easy.

[fr499y]

always fishless cycle.

https://www.aquariumforums.co.uk/viewtopic.php?t=8002

[Bluetaurus]

Hello and welcome
As above, fishless cycle is the way to go.
Very good guides on here to help. Patience is needed because it can be frustrating waiting to add fish.

[Martinspuddle]

Greetings & welcome to

[black ghost]

That shop will kill your fish in no time. Please don't go back there. The online advice isn't much better.
Fish-in cycling is always harmful to the fish involved. It makes them suffer but not die, which some people are ok with, but isn't right.
Cycling is easy. Read the guide fr499y linked.

[Martinspuddle]

I'm wondering if with the title 'Can you cycle a small tank (fish-in) in a week?' has the OP has already got fish?

Seems to me aquatic stores are only interested in one thing, making a profit.

[plankton]

Welcome to the forum.
If you already have fish then use something like Tetra Safestart or Seachem Stability alongside the water changes to help build the "munchers" in the filter to cycle.
If you don't have fish, the fishless is always the better way to go.
Certainly what the shop told you is offensive, especially to fish.

[bensmithuk]

Thank you for the warm welcome and the gentle advice.

We do have fish in the tank now. It is 8 weeks old and we have 1 Betta and 2 Neon Tetras in there - we started off with 6 Tetras but lost 4*.

I *thought* we had cycled the tank but either (a) I was wrong or (b) some accidentally non-conditioned water (3 of the Tetras died within 48hrs of this) crashed things.

For at least 3 weeks we've been at:
0ppm Ammonia (all the time)
0.25-0.5ppm Nitrite
Up to 40ppm Nitrate

I was doing 25-50% water changes every time the Nitrate got to 40ppm or more. That was nearly daily at one point, but my local store tells me this is preventing the Nitrite > Nitrate part of the cycle from completing and I should let Nitrite spike.

I'm adding bacteria (Nite-Out 2) daily whilst the tank is uncycled.

I wish we'd done a fish-out cycle now but were led by a long and very detailed chat with local store as the online info was overwhelming and seemed inconsistent.

* I'm aware theTetras need to be kept in groups ideally more than 6 but not adding any more fish until tank is ready.

[fr499y]

anything above 0 for nitrite is deadly to fish, so no.. never let the nitrite rise. as soon as you detect some in the tank, do a water change.

Also 25L is too small for tetras and is more suitable for the single betta on its own