The Dutch translation of this article is by DeepL Translate, it can be inaccurate, incomplete and probably with some of errors! But much better than Google Translate

2.4.1. Dr. Tim’s Cycling Method

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Author : David Bogert

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8 minutes
Difficulty : Level 7

Excerpt :

This delineates the procedure Dr. Tim recommends for cycling an aquarium filter with pure ammonia.
One of the more popular methods of cycling is to use Dr. Tim’s ammonia solution. We do not agree with the methods of Dr. Tim but his method will work. It will just result in an aquarium that cannot handle very many fish in the beginning.

Here is an analysis of Dr. Tim’s method:

The directions on the bottle of Dr. Tim’s ammonium chloride solution are:

“Add 4 drops of solution per gallon to achieve an ammonia-nitrogen (NH₃-N) concentration of 2 ppm. Do not exceed 5 ppm in the aquarium”

In Dr. Tim’s videos, he clarifies these directions with the point NOT to add ammonia every day. Rather test the water and only add ammonia when the concentration drops below 0.5 ppm. This will typically be about every five days initially, then it will drop to every day. Then when it drops to zero after 24 hours Dr. Tim says one’s aquarium is cycled.

Note we do not agree with the directions. Dr. Tim explains in his videos that the “Do not exceed 5 ppm in the aquarium” directions are “because his research says nitrifying bacteria are inhibited above 5 ppm ammonia“. Dr. Tim supposedly bases his directions about not exceeding 5 ppm on a paper he co-authored (“Identification of Bacteria Responsible for Ammonia Oxidation in Freshwater Aquaria”, Timothy A. Hovanec, et. al. 2001).

This paper said that bioreactors culturing beneficial bacteria at a concentration of 5 to 10 ppm gave a different species profile of bacteria that reactors kept at 40 to 60 ppm ammonia. This paper ONLY looked at these two levels, 5 to 10 and 40 to 60.

picture of an aquarium fish Maylandia lombardoi (kennyi) male
Maylandia lombardoi (kennyi) male

This study did not look at the ability of these different strains of bacteria to oxidize ammonia. This study did not say that the strains of bacteria that grow best at 40 to 60 ppm of ammonia will not oxidize ammonia at 5 to 10 ppm concentrations. This concept was never tested, even though it would have been easy to do. This raises questions as to the purposes of the whole paper. Is it deliberately slanted? In any case, the conclusion that a maximum of 5 ppm ammonia during cycling in an aquarium is necessary simply is not supported by this study.

There were NO studies done at the middle concentrations and a maximum of 5 ppm wasn’t even tested, 5 to 10 was the parameter in the study. So once again the conclusion that a maximum of 5 ppm ammonia during cycling in an aquarium is necessary simply is not supported by this study.

This study was published in a journal but was done by a private company (apparently Dr. Hovanek’s Company: The Aquaria Group, Moorpark, CA). This type of “research” is always suspect, no matter how scientific it looks. The profit motive can color the outcome. This company sells bottles of beneficial bacteria and claims very rapid cycling. The lower the ammonia input the “faster” the “cycling” simply because there is less ammonia to be removed (although, surprisingly, testing showed this was not the case!).

picture of an aquarium fish Maylandia mbenjii (Zebra red top mpanga)
Maylandia mbenjii – Zebra red top mpanga

Note also that this Hovanek study used a cylinder filled with ammonia-filled water and stirred to produce a “biofloc” in the water column consisting of beneficial bacteria in a “mulm”. They did not use stationary media such as is found in an aquarium filter to cultivate the beneficial bacteria. This study also added potassium phosphate as part of the process, in addition to ammonium chloride. So the whole applicability of this study to aquariums becomes very questionable.

In actuality, University research shows the optimum levels of ammonia and nitrite are about 200 to 400 ppm for cultivating all strains of beneficial bacteria (Lewis 1958, Olah 1993, Tappe 1996, Willke 1996, Du 2003, Gibbs 1919, Grzesiak 2017, Kasmurik 2018).

Peacock Yellow Hybrid
Peacock Yellow Hybrid

So I would add four drops (about 2 ppm) of Dr. Tim’s ammonia per gallon (3,79 liter) every single day. The more beneficial bacteria you have the more resistant your tank is too sudden ammonia spikes from the likes of a dead fish. And after the aquarium is set up and filled with water add a quarter teaspoon of a phosphate powder (potassium phosphate, sodium phosphate, or any one of several calcium phosphates, or a high phosphate “bloom” fertilizer like Scott’s Super Bloom 12-55-6, Flower Fuel 1-34-32 or Miracle-Gro Bloom Booster 15-30-15) per twenty-five gallons of water. This is beneficial when cycling with ammonia.

Note this recommendation is somewhat dependent on the filtration. A small in tank cartridge filter can take eight to ten weeks to cycle with four drops per gallon (3,79 liter) per day, if it ever cycles. With poor filtration Dr. Tim’s advice to not exceed 5 ppm is probably sound simply to keep the time to cycle somewhat reasonable, like four weeks. A good filter, like a properly sized sponge filter, will cycle faster with 4 drops per day.

picture of an aquarium fish Maylandia msobo magunga
Maylandia msobo magunga

Test of Dr. Tim’s Instructions

To test the claim by Dr. Tim that one should only add ammonia when the level of ammonia drops to below 0.5 (i.e. 0.25) a test was run. This is the test:


A test was run to see what ammonia additions are best for cycling an aquarium. The test showed one thing:

  • The test showed using Dr. Tim’s regimen of only adding ammonia when the level hits 0.25 increased the time to cycle by 11 days

Note that this test was deliberately kept quite simple so that anyone can easily duplicate it if they want to. A rigorous scientific test under laboratory conditions cannot be replicated by any hobbyist so that was not done. This test was not designed to be published in some scientific journals. But the huge difference in the test results makes the conclusions unmistakable and very valid, even if the science is not as rigorous as some would like.

Maylandia zebra Gold Kawanga
Maylandia zebra Gold Kawanga

A caveat has to be noted here. These tests were run in the same room that held several functioning breeding and quarantine tanks that had bubble aeration from air stone-operated sponge filters. These airstones would have produced what is called an aerosol of water droplets that contained beneficial bacteria. This bacteria would have slowly inoculated all of the experiments below.

Test Equipment:

  • Home Depot five gallon (20 liter) buckets
  • 100 grams BASF ammonium chloride dissolved in one gallon (3,79 liter) of distilled water
  • air pump and airlines
  • mini sponge filters
picture of an aquarium fish Maylandia Pyrsonotos Red Top Zebra (Nakatenga)
Maylandia Pyrsonotos – Red Top Zebra (Nakatenga)

Test Procedure:

6 buckets were set up with reverse osmosis water. A pinch of potassium phosphate was added to each bucket. Then two drops of ammonia liquid per gallon (about 2 ppm) were put into the water every single day. We did no water changes.

The water was naturally about 6.8 in pH 0 KH after sitting for a week to stabilize.

  • Three buckets had nothing done to them (the “controls”) with 2 ppm ammonia added daily. The ammonia level in this bucket went to peaks of roughly 10, 8, and 14 ppm ammonia (testing by dilution).
  • Three buckets had 6.8 pH and ammonia added per the directions of Dr. Tim, i.e. only add ammonia when the ammonia level drops to 0.5 to 0.25.

The buckets were then cycled. The buckets were then tested every day for ammonia and nitrite.

Maylandia zebra Likolma
Maylandia zebra Likolma


Defining zero (technically it is less than or equal to 0.25 ppm) ammonia and nitrite for two days (two readings) as being cycled, the following results were obtained:

Cycling Test Dr. Tim's regimen
Cycling Test Dr. Tim’s regimen

This test showed that Dr. Tim’s regimen of ammonia additions produced a cycle time that averaged 11 days more than adding 2 ppm daily of ammonia. This is not surprising. Beneficial bacteria, like all primitive organisms, reproduce at a rate directly proportional to the food supply. Dr. Tim’s regimen means roughly 1.1 ppm of ammonia is in the tank on the average while the 2 ppm regimen ensures a rise to over 10 ppm followed by a fall to 0.25 ppm in the tank, probably an average around 6 ppm. So the 2 ppm regimen goes faster.

Maylandia zebra Maison Reef
Maylandia zebra – Maison Reef

Ammonia Cycling Where the Feed Stops

For reasons I have yet to elucidate, some folks on social media stop the addition of ammonia and then declare their tank “cycled” when the ammonia and nitrite drop to zero after a considerable length of time. They then come back on social media asking what happened when they added fish and got an ammonia spike. They are typically using Dr. Tim’s ammonia but I haven’t been able to find any videos supporting how they do their cycling. This is a graph one of them posted:

Chart on cycling aquarium
The chart on cycling aquarium

They STOPPED FEEDING ammonia after one week. Then, after three and a half weeks, the individual declared their tank “cycled”. Yes, for very low levels of ammonia their tank was technically cycled. But if they were a typical newcomer and added too many fish or overfed, they will get an ammonia spike for sure. One MUST continue to add ammonia regularly to properly cycle an aquarium.

Maylandia masinje Zebra
Maylandia masinje Zebra

Note also that the whole cycling “science” is a natural process. There are hundreds of variables that one cannot control. So sometimes one can cycle in days and sometimes it can take months, no matter what one does. Mother Nature is just not very predictable.