Has this tank cycled...

[pahansen]

Hi. We set up our first tank, 20 gallons, in July. The first fish (two cherry barbs) went in on July 12. I have not noticed any real change in the nitrate and nitrite levels of the tank since we started. We are using my aunt's old tank, but I can't believe it's possible that the bacteria have survived almost 20 years without water!

The current levels are:
NO3 - ~20 (or less)
NO2 - 0
Hardness - 120
Alkalinity - 0
pH - 6.4

These numbers have remained virtually the same in the four weeks we've had the tank. We've added a small pleco (2"), but none of the numbers have changed. Shouldn't we have seen a spike by now, or at least the beginnings of one? Could this have anything to do with the hardness or low pH of the water? I have been hesitant to mess with the pH, alkalinity, or hardness since the three fish all seem happy and healthy.

Also, I haven't really been cleaning the gravel, thinking that might help the tank to cycle. I've just added water when necessary and cleaned the glass and tested to make sure the fish were okay.

We would like to add a few more fish to the aquarium eventually, but we don't want them to die from a sudden nitrogen spike. On the other hand, maybe we need more fish to get the tank to cycle. At this point we're wondering if we have some sort of magic cycling tank! Any thoughts?

-- Pamela

 

[yhbae]

Given that you added the fishes over a month ago, and the fact that you have nitrates mean you have the bacteria in the tank. Are you SURE that you have never observed any levels of ammonia and nitrite during the past couple of weeks? It sure sounds like your tank has been cycled...

 

[pahansen]

I tested the water every two days for the first three weeks (just waiting for something to happen!), and the highest NO3 reading I got was between 20 and 40. That was two days after we put the fish in. Since then the No3 readings have consistently been 20 or lower.

The NO2 level was .5 for the first six days of the tank setup, then it's been at 0 ever since.

But the weird thing is that the NO2 level was .5 even before we added fish, and the NO3 level was at 20 before fish as well. So fundamentally, my table of testing results looks like a carbon copy, beginning to end.

So hopefully you're right, and the tank is cycled. At least now I know I'm not crazy to think it is!

When do you think it's safe to add another fish? The pleco went in two weeks ago.

 

[yhbae]

You must have had some source of ammonia before adding your first fish. How long was the water sitting in your tank before addition of your first fish?

 

[pahansen]

Mmm... let's see. Set up the tank one night, filled the tank while hubby was at work the next day, picked up the barbs that evening after dinner. So maybe 5 or 6 hours.

I'm trying to think what went into the tank. Gravel, which I rinsed well, two pieces of driftwood, and a few plants, which I treated with permangenate. But I think that should be safe for the tank.

Oh well, I guess it doesn't matter, now that the ammonia is gone. And I'll only be setting that tank up once! But it's a bizarre mystery. Perhaps someone used some sort of cleaner in it that left residue? It was a hand-me-down tank that hadn't been used for over a decade.

 

[yhbae]

Well, whatever happend there, you have the right results! No ammonia, no nitrite and significant amount of nitrate....

Hmm... Just realized something - does your tap water contain any nitrates by any chance?

 

[pahansen]

Yep. How about that. Nitrate levels in the tap water are about 20. So does that mean that the bacteria were already there when we started?

 

[paulioo]

I could mean that your tank may not be cycled and the nitrates that your seeing in your test results are coming from the tap water. But given that your fish have been in the tank for a month and still there is no ammonia readings probably means that your tank is cycled.

In short, your tank could well be cycled or it could still be waiting to cycle

Why did i post this... totally pointless....im off to lie down

 

[sinistral]

How many plants do you have and what kinds?

EDIT: I ought to explain what I am thinking. There are quite a few articles floating around the web on cycling a tank with plants. Plants can help a cycle along in two different ways. They preferentially use ammonium ion for metabolism (Secondarily, they will use nitrates. As far as I know, they do not use nitrites). Secondly, they typically will come "pre-seeded" with beneficial bacterial colonies.

This has several implications, mainly that plants will compete with beneficial bacteria for ammonia. It is likely that, depending on how heavily you've planted, you may never see an ammonia spike. Bacteria will convert some ammonia (a relatively small proportion given that much of it is utilised by the plants) to nitrites; hypothetically this is converted to nitrates by the bacterial colonies present on the plants. For this reason you may never see a nitrite spike either.

This is a link to an article on cycling with a heavily planted tank. One side note is that I believe that Chuck Gadd's contention in this article that plants use nitrites is incorrect.

Here is a link to a post on the fins.actwin mailing list archive. It's just a blurb, but it talks about the benefits of heavily planted cycling in terms of outcompeting algae.

Finally, I have observed this phenomenon myself in my 10g planted tank. I cycled it with regular fish food. At the time it was between "sparsely" and "heavily" planted (medium, I guess ). To my surprise, I did actually see low nitrites within a week (I wasn't expecting anything for a month), and they quickly dropped to nothing.

As a caveat, I don't yet know how heavily planted your tank is, so this all could be fruitless speculation on my part. Hope that helps~

 

[pahansen]

There are currently about 6 stems of anacharis, which have really taken off, and 8 stems of moneywort (not pennywort, as I mistakenly wrote elsewhere) which look rather scrappy. I don't care for the moneywort as much as I'd thought I would and am thinking of replacing it with something else.

There were also two nice sword plants in there in our pre-pleco days, but those turned into skeletons pretty quickly!

I'm looking at adding some Java fern and anubias, if I can find the anubias locally, and tossing the moneywort.

 

[sinistral]

Please see my above edited post...I would bet that with all that anacharis, bacopa, and the fast growing swords the phenomenon I was describing has happened to your tank.

 

[pahansen]

It makes sense, particularly the part about the plants coming with their own bacteria supply. That's probably what happened. We'll see if things change with new fish, but really -- the thing has been so stable so far...

Thanks for the info and links.

 

[ketyana]

Stupid to say I know, and by now Im sure the cycle should be over anyways, but if you are using the same test kit for all, for example a strip test kit with all the reading on one stick or a box set with out of date chemicals etc could be the test kit is screwy get the reading double checked at your LFS

Infact do this anyways, no harm in a second opinion