Fishless Cycle - confusion over water testing results so far …. Pet of the Month
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New Member
Dec 3, 2022
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Hi guys

So I started a fishless cycle 5 days ago and the results I am getting so far are confusing me a little so looking for a little help?!

I de-chlorinated using Tetra “aqua safe” then once water was up to temperature I used Dr Tim’s “one and only live nitrifying bacteria” and ammonium chloride. I also used a gel “filter starter” with live bacteria.

I have followed all instructions on the bottles and made sure correct quantities of any products are added (live bacteria apparently unable to overdose with).

The confusion is being caused by the readings not being what I’d expect during a cycle (or what I think I understand they should be doing - firstly spike in ammonia, followed by spike in nitrites and fall of ammonia, finally followed by increase in nitrates and fall of nitrites). I also understand it is very early days in terms of cycling process - however the results I’m getting don’t make sense to me - ammonia levels not dropping and already getting high nitrate readings.

I will list my daily test results below along with my tank and filtration system details. I’ll also add a picture of the current bacterial bloom I’m experiencing.

Any advice or explanation of what you think is going on and what to do next would be much appreciated.


Tank: Fluval Siena 270 - 270L/60gal.
Filter: Fluval 307 canister filter - I have removed chemical filtration included with the filter and added an additional 500g Fluval Biomax and 500ml Seachem Matrix.
Sand substrate
Dragon Stone aquascape - no plants just yet but live plants to be added soon.
Temperature: 23C

Pro JBL Aquatest combo set - water analysis

Day 1 - 270 drops of Dr Tim’s ammonium chloride added (1 drop/L as per instructions to equal 2ppm concentration). 240ml Dr Tims One and Only live nitrifying bacteria added.

Day 2 - pH 8; NH4 = 1ppm; NO2 = 0.1ppm; kH 11dH

Day 3 - pH 8; NH4 = 1ppm; NO2 = 0.2ppm

Day 4 - pH 8; NH4 = 1ppm; NO2 = 1ppm or more (my test kit only measures nitrite your to 1ppm) - bacterial bloom started.
Extra ammonium chloride added (equal to 2ppm).

Day 5 - pH 8; NH4 = 1.5ppm; NO2 = more than 1ppm; NO3 = 30ppm


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Aiken Drum

New Member
Oct 3, 2022
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Most nitrate test kits will show nitrate as a false positive if there is nitrite in the water. Dont even bother testing for nitrate until you are cycled and there is no nitrite because the test results will be confusing.


New Member
Jan 26, 2023
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Agreed with Aiken. It is still early on, so things are likely to be out of whack whilst it balances out. Try to sit back and let nature take its process. Adding any extra ammonia will throw things out of whack. I would test it and make sure it doesn’t exceed 4ppm. If ammonia reaches over that level, it’s detrimental to the nitrogen cycle (I found that interesting). Sorry if this item is listed already, but do you have an air stone running? If not, considering using one long term in your aquarium. Bacteria needs oxygen to grow and thrive


Fish Connoisseur
Dec 31, 2004
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I only have questions and then a few comments. But first, Being a Yank, I work in gallons. So you will need to multiply my numbers below by 3.78.

What size tank do you have?
Whose method of fishless cycling are you following? You should have been following Dr. Tim's which is on his site.
What are your tap parameters for pH, Kh and GH

Next, you have made a few mistakes which most folks new to the hobby make.

First, Dr. Hovanec is a scientist. As a result he uses a different test scale than is used by hobby test kits. He measures using the nitrogen scale while our kits usually measure on the Ion scale. In a nutshell that means we have to convert his numbers to ones which match out test kits. So have a look here

Next, you were on the right track until you added the gel stuff. That should have been left in the store. It is likely why you have a bacterial bloom. Most bacterial starter products do not contain the strains of bacteria which will ultimately colonize our tank. That means the wrong ones must die off and they can be food for a bacterial bloom. But so can too many nutrients in the water from other sources.

A fishless cycle without the use of one of the few viable bacterial starter products normally takes about 5 weeks and involves adding ammonia several times during the process. On the other hand, using a one of the two starter products I recommend should shorten the time to under 2 weeks and the test results along the way will be completely different that in the plain vanilla cycle. The bottle of bacteria should contain both ammonia and nitrite oxidizing bacteria. In the normal fishless cycle ammonia bacteria must colonize first and then the nitrite ones will follow.

Based on the amount of ammonium chloride you added I would think you have at least a 75 gallon tank. The volume of a tank when we buy it does not mean the tank will hold that amount of water. For one we do not fill to the top of the glass. Next, we add decor and substrate etc. all of which displaces water thus reducing the volume from what is advertised. I normally suggest folks use about 85% of the advertised volume. More if there is ton of decor and substrate and less if it is a bare bottom tank with only a few decorations.

The original Dr. Tim's ammonium chloride used to be stronger and it required only 2 drops/gallon. I have used this and his bacteria now for 20+ years. I dose his ammonium chloride in ml at the rate of 1 ml/20 gals (75.6l). That makes it easier especially at one is using it for a bigger tank.

edited for typos and spelling
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