Cycling with fish - nothing happening?

[mtrel]

I started a 75 gallon tank a month ago with 4 tetras and 2 zebra danios. I did this based on advice from the pet store. Unfortunately I found this forum later and now know that this is not the best way to do it. I've been testing for ammonia only about once a week and levels have never been above .50 ppm, usually less. The last pwc I did was a week ago. Today I tested ammonia, nitrates and nitrites and all are 0. This is the first time I've tested for nitrites and nitrates so I don't know where I am in the cycle. Can someone give me some advice on where to go from here? Is it possible that the cycle never started or it completed already?

[BillD]

If this tank were cycled it would show some nitrate (normally) as well as 0 nitrite. That is a very light load for a tank of that size, so that could be the reason for so little showing. There is very little to provide enough ammonia to feed a full colony of bacteria, so while it may be cycled for the fish that are in there, it will not increase the bacteria for a bigger bioload, until you increas the bioload by adding more fish. Adding a few more fish will give you a better idea. If you are using strips to test, they are notoriously innacurate.

[mtrel]

I am using the Aquarium Pharmaceuticals master test kit. If I were to increase the bioload what other kinds of fish could I use besides tetras and zebras? Should I just add a couple of fish at a time until ammonia levels start forcing me to do pwc's?

[Purrbox]

Also if you have any live plants in the aquarium that could account for the non existant Nitrate readings. If not I'd be suspicious of your test results. It's be worthwhile to double check the instructions to ensure that you haven't inadvertantly made a mistake while testing.

That being said you do have a very small bioload for such a small aquarium. I wouldn't recommend adding fish until you have to do water changes, as this would be very stressfull on the fish. Rather you could continue to add fish slowly and may be able to avoid the worst of the cycling issues.

[patryuji]

Keep an eye on your nitrates for the next 2-3 weeks. You might get some low levels coming up (it is just taking time for your very small bioload to build up an appreciable and easily measurable amount of nitrites & nitrates given the size of the tank).

Although cycling with fish isn't a good idea ...given the volume of water and how few fish you should be okay. I don't think you are done cycling (unless you have plants as others mentioned). If you don't have plants give it another 2-3 weeks and keep measuring nitrites and nitrates. I wouldn't put any other fish in the tank yet [if you don't have live plants].

[TomK2]

mtrel:

You are doing great! Your LFS gave you some good advice, without a good background explanation. I have a web page that explains my "go low, go slow" philosophy. I just havent been around in a while to promote it. Check out

Low Bio-load

I think that you can add some bioload in a tank that size. The trick is to go very slow. Imagine your bacteria growing on levels of ammonia well below your test kits lower limit. Yes, they do grow and thrive at less than 0.25ppm of ammonia, after all, once the cycle is done that is situation normal! Your goal is to have the fish bioload adding ammonia to the tank so slowly that bacterial growth can keep up, and keep the ammonia below 0.25ppm.

Take a look at my web page. You will probably want to add a few inches of fish, then wait a week or two. Then a few inches more. Around 45 days or so, if you have not been doing water changes, I bet you start to see your nitrates creep upwards without seeing a spike in ammonia or nitrite.

[mtrel]

Thanks for the advice. I don't feel so bad cycling this way after all. I guess the size of the tank and taking things slow isn't so harmful. I never saw any detectable nitrites and ammonia never even came close to .25 ppm. I added 2 gouramis and 2 corys about 18 days ago which brings the total of fish up to 10. Today I have about 5 ppm of nitrates, 0 ppm of nitrites and ammonia is close to 0. I had a lot of brown algae but that seams to be dying off now. I just did a 20% water change since I needed a gravel vac. I'll see how things go over the next few days.

I was wondering about changing filter media. I've had this tank up and running for about 6 weeks and have not changed anything yet. I'm running an xp3 and I am assuming because of the bacteria needed I should not change all the media at once. For example, should I change the course material one week and then the medium and fine a couple weeks later so the course material can build up the needed bacteria?

[neilanh]

There's no real need to change out that media. WHen you do a PWC, capture some of the water in a bucket, then use that tank water to rinse/clean your filter pads. Get out all you can from them in tank water, that will clean your system and preserve your bacteria.

I've been running the same filter pads for over a year with just routine cleanings like I described above.

[TomK2]

If the filter stuff is not dirty or clogged, leave it in place. When you do change media, never change it all at once. I am not familiar with your filter, so I can not comment specifically how to go about changing things. But if you have sponges and floss upstream of a porous biomedia (such as ceramic noodles or porous rock), you can clean/change the sponges and floss as long as you leave the porous media intact. In effect, the spnoges and floss are there to keep the porous media clean, it is the porous media that is the substrate for the beneficial bacteria (not that the bacteria don't grow on the spnges and floss too). Until you are certain, leave the filter alone unless it is abviously dirty or clogged?

I have noticed that the brown algae (diatoms) seemed to preceed the the end of the cycle by a week or two in the last two tanks I started from scratch. Tap water can have nitrate, so you need to see nitrate increase over baseline tap levels to be sure.