There are many ways to successfully cycle an aquarium:
- The ammonia “feed” can be fish food, chopped meat, milk, baby food, chemical ammonia, ammonium chloride, or even urine.
- You can add a large amount of feed like a whole shrimp in a sock or you can add small amounts of “feed” over time.
- The beneficial bacterial “seed” can be nothing, soil, filter media from an established aquarium, composted manure, brown gunk squeezed from a sponge filter, or potted aquatic plants.
- Some people add no fish, some add feeder goldfish, gouramis, or danios. Many even add their expensive fish and do the cycle around them (most of the time inadvertently!).
- Some people add plants, and some people do not add plants. Both ways “work” just fine.
- Some people test everything once a day or more while some never test anything.
This is far from an exact science and many things “work”. Some things can indeed speed up a cycle and some things slow down a cycle, but in the end, just about anything will “work”. Mother Nature is very flexible and forgiving.
If one is interested in getting the fastest possible cycle this cycling test done by the author might be of interest:
| Treatment | Average time to cycle | Aquarium1 | Aquarium2 | Aquarium3 |
|---|---|---|---|---|
| Food + urine + phosphate | 23 | 18 | 26 | 26 |
| Food + urine | 25 | 28 | 22 | 26 |
| Ammonia + phosphate | 25 | 32 | 20 | 24 |
| Only ammonia | 35 | 42 | 30 | 32 |
| Dr. Tim’s + phosphate | 36 | 40 | 33 | 36 |
| Ammonia + Prime + Stability | 37 | 38 | 30 | 43 |
| Only Dr. Tim’s | 43 | 48 | 38 | 42 |
The complete details of the testing which gave this chart can be found at this link:
2.13. Cycling Test
Note there is no use for Prime or other chemical additions during cycling. You can’t “detoxify” ammonia with chemicals. More about that in:
2.9. Instant Cycling with Chemicals
And a test was run on nine different “bacteria-in-a-bottle” which showed they were a waste of money. This link reviews that test:
2.8. Bacteria in a Bottle
Definition of Cycled
The term “cycled” in the aquarium hobby has two distinct meanings. The most common definition is that a cycled aquarium has large colonies of beneficial bacteria that can handle a decent-sized ammonia load from a decent-sized number of fishes. But there is a second meaning, namely an aquarium that can handle the ammonia load of a decent number of fishes. If an aquarium has many plants, the plants can function as beneficial bacteria, giving an aquarium without sizable colonies of beneficial bacteria that can still handle decent numbers of fish.
This dual meaning can create problems when someone claims something along the lines of “I put a ton of fish in my uncycled aquarium and didn’t have any ammonia spike”. Another commonly heard anecdote is “I put XYZ brand of bottled bacteria in my uncycled aquarium with a ton of fish and never had any ammonia or nitrite spike”. Both these people will typically have an aquarium with plants in the scheme. Plants absorb ammonia.
The other common problem with defining a cycled aquarium is the level of ammonia it can handle. Most hobbyists aim for an aquarium capable of handling 1 ppm of ammonia every 24 hours. But some on social media aim for only an aquarium that can handle 0.25 or 0.5 ppm of ammonia. These hobbyists get faster cycle times, of course, but they run the risk of sizable ammonia spikes if they add any decent number of fish.
One Myth: An Aquarium MUST be cycled Before Adding any Fish
There is a myth that if one adds moderate numbers of decent-sized fish to an aquarium that isn’t cycled, the fish will die a good percentage of the time. Because of the low toxicity of ammonia and nitrite, one CAN successfully add moderate numbers of decent-sized fish to an uncycled aquarium (and many experienced hobbyists do just that).
There are some caveats:
- It must be a small number of small fish.
- One can’t overfeed (greater than 1% of the fish’s body weight per day).
- The higher the pH the worse the problem with ammonia (going from 7.0 pH to 8.0 pH increase the ammonia toxicity by a factor of ten)
- A lower pH (6.5 and lower) can present a problem with nitrite
Even if these caveats are broken the fish typically don’t die. They just in theory (per many research papers) can sustain organ damage which will shorten their lives.
There is a good reason fish-in cycling can be made to work. Ammonia and nitrite are nowhere near the killers many would have us believe. The acute toxicity of various compounds in the aquarium is as follows (pink numbers):
| pH of the water | API Ammonia test in ppm | Api nitrite test in ppm | |||
|---|---|---|---|---|---|
| pH | Alert | Alarm | Toxic | Alarm | Toxic |
| 6.6 | 16 | 64 | 160 | 0.5 | 2 |
| 6.8 | 11 | 44 | 110 | 0.5 | 2 |
| 7.0 | 8 | 32 | 80 | 1 | 4 |
| 7.2 | 5 | 20 | 50 | 1.5 | 6 |
| 7.4 | 3 | 12 | 30 | 2 | 8 |
| 7.6 | 2 | 8 | 20 | 2 | 8 |
| 7.8 | 1 | 4 | 10 | 2.5 | 10 |
| 8.0 | 0.8 | 3 | 8 | 3 | 12 |
| 8.2 | 0.6 | 2 | 6 | 3.5. | 14 |
| 8.4 | 0.4 | 2 | 4 | 3.5 | 14 |
| 8.6 | 0.25 | 1 | 2 | 4 | 16 |
| Nitrate alarm level is greater than 80 ppm. Nitrate tocix level is greater than 440 ppm. |
|||||
To read the ammonia and the nitrite levels on this chart find the pH of the aquarium first. Then find that pH in the left column. Read across as to the levels the API tests will show. Green is the “Alert” level where increased testing is called for, yellow is the “Alarm” level where one should do a 50% water change. And “Toxic” is the level where one should do a 75% water change. Note many of these levels require diluting the aquarium water with 9 parts of distilled water. Test the diluted water. Multiply the results by ten and you have the levels in the aquarium.
Ammonia and nitrite are just not as toxic as some would have us believe, especially if the exposure is only for a few days. So even the much-maligned “fish-in” cycling works well 95% of the time.
This will raise some huge howls of protest but the numbers are solid and the papers supporting these numbers can be found in this link:
5. Ammonia, Nitrite, Nitrate, and Chlorine
Cory of Aquarium Coop recommends cycling with fish in the aquarium for the beginner. He is a very knowledgeable and experienced fish keeper (I think he is THE MOST knowledgeable in the business!) so one must pay attention to what he says. Cycling with fish is just easier for a novice to understand and do. If one adds too many fish, or if one adds too much fish food, the water can become too laden with bacteria and the fish can get the disease as a result. But this is probably much rarer than social media would lead us to believe.
2.5. Fish-in cycling
Other ways to cycle are covered in these links
2.1. Standard Fish-less Cycling
2.3. How I Cycle a Tank
2.4. Cycling with Ammonia
2.6. Not Cycling at All
Startpage Aquariumscience
Source: Aquariumscience.org – David Bogert
