[NinaS]

I've been cycling my aquarium for 3 weeks now with the use of bacteria from an established tank as well daily dosages of ammonia. My tank can now fully break down 2ppm of ammonia, with a small reading of about 0.25ppm of nitrite in 24 hours, with the nitrite breaking down to 0ppm within the next 12 hours.

So I went to my LFS to get a small school of cardinals (possibly neons), but the guy at my LFS was extremely reluctant to sell me cardinals because he said that there would definitely be an ammonia spike regardless of my fishless cycling, and that your tank can only cycle once it has a constant source of food from fish waste, regardless of any 'chemicals' I have added to my tank. He basically said the only way to properly cycle a tank is with fish, even though I explained that I had dosed my tank with ammonia daily for 3 weeks, as well as adding established filter media.

In the end I ended up buying 9 'Hardier' neons.

I was just wondering, will there definitely be an ammonia spike regardless of fishless cycling, and is the only way to fully cycle a tank, with fish? Is what he said true? It's just I had read differently elsewhere from multiple sites.

In any case it's nice to know my LFS have the fish's health in mind.

My tank is 60L/15g.

Thanks!

 

[Dave-H]

I don't think there is a clear answer about whether there would be a spike or other fluctuation, but I think that in theory the ammonia from fish is the same that you would use from the ammonia in a bottle. So, whenever you change things, like when you add fish, it will fluctuate.

But, does that matter at all? It seems like it's not worth worrying about, to me. If you cycle your tank using 2 or 3 hearty fish, then add a school of cardinals there will be some fluctuation. If you cycle your tank fishless, than add a school of cardinals there will be fluctuation unless your fishless cycle approach used the exact same amount of ammonia that the fish will produce -which is unlikely.

All that really matters is that you get your bacteria going and established enough so that when you add the fish, you can handle any fluctuations via water changes and the system will stabilize quickly without endangering any fish.

Beyond that, it doesn't really matter and what does it mean to 'fully cycle' a tank anyways? I think it's not a very nuanced response from the LFS.

In my view, whenever you add fish to a new tank you can expect fluctuation in the ammonia levels while the bacteria and the fish waste fall into some kind of balance. During that time, do more substantial and frequent water changes to ensure that the ammonia levels don't spike in a dangerous way, and slowly settle into a more regular schedule and everything will be fine.

 

[NinaS]

Thank you very much!

I am of course disappointed to have got neons instead of cardinals, and like I said to the guy I didn't want to get hardy fish now for me to not want them in there later on. But my neons do in fact look striking, and their smaller size makes my tank look larger!

I will keep a close eye on the ammonia and nitrite levels. I just tested the water and (it's been about 16 hours since I added them) ammonia is at 0ppm, as is nitrite. If there probably will be a spike, when is it likely it'll happen?

 

[bikinibottom]

From my (limited) understanding, cardinal tetras are much more sensitive than neon tetras, and thus need as stable conditions as possible. While I think your LFS is right to dissuade you from getting those fish with a very new tank (because yes, there will be more ammonia when you add the fish, and your newly established bacterial colony will be greatly put to the test), I think the reasoning is wrong -- you don't need fish waste to cycle a tank. Ammonia is ammonia is ammonia, and the bacteria does not discriminate whether it came from a bottle or a fish. I think what you need is just time, and that in another month or two your tank will be more mature and better able to handle whatever spike in ammonia may occur, and thus the health of a more sensitive fish won't be put at risk.

 

[DarkCobra]

+1 wrong.

There's an easy way to solve this, right in the store. Ask the employee how fishless cycling using ammonia as they're familiar with it is typically performed, and why they feel it doesn't work. Don't explain how it works, and provide as few other details as possible.

Chances are they won't be able to provide any details of their own. In which case they're simply unfamiliar with it, and have no business providing an opinion on it. And sadly, it's then usually best to lie and say something like "you're probably right, I have another cycled tank I can move some fish out of to make room", rather than have them deny you the fish, or a warranty. Don't count on being able to educate such people or change their minds, I've even heard of people who stuck to their guns banned from an LFS by ignorant employees.

If however they are capable of describing it in some detail, then perhaps they know something you don't, and it's worth double checking.

This works for anything, not just fishless cycling.

 

[Gomer]

Fishless cycling with ammonia, or other nitrogen sources (like urea,...but not human pee. that is disgusting and inappropriate. Other animal urine is fine, normal and appropriate) is done explicitly to prevent the spike. The only way you would get a spike after fishless cycling, is if you cycle with a tiny bit of ammonia, and add a bunch of fish.

 

[Sluggo]

You asked for Cardinals, which should have indicated that you wanted to keep a warmer tank. The guy sold you Neons, which like cooler water. Now you're stuck with them, and he has limited what else you can keep in the future, all because he doesn't know anything about fishless cycling. Sweet.

 

[NinaS]

You asked for Cardinals, which should have indicated that you wanted to keep a warmer tank. The guy sold you Neons, which like cooler water. Now you're stuck with them, and he has limited what else you can keep in the future, all because he doesn't know anything about fishless cycling. Sweet.

I was pretty damn annoyed if I'm honest!

The neons are beautiful, but I just love the deep blue and the bright red of the cardinal.

There has been a tiny ammonia spike so far, that was just barely picked up by my test kit, not quite 0.25ppm, just a tiny bit more than 0ppm. It has not gone up nor did any of my fish seem to be affected by it. It was so small it did not register any nitrite however now there is 0ppm of ammonia, and 0 nitrite. I will test regularly to see if in fact my LFS were correct. But so far there isn't much evidence backing them up.