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Sulphur Denitrator Break in / Cycling – Step By Step

Posted on Tuesday, May 4th, 2010 at 5:18 pm by

The intent of this article is to document the cycling period of a sulphur denitrator using digital read outs using a Pinpoint nitrate monitor. A simple, 60 gallon FOWL system was set up using only live rock and a maxi mod. The nitrates were allowed to climb to 29ppm.

Here is a photograph of the tank showing the denitrator on the right side.


The initial reading of the nitrates in the aquarium was 29 ppm. When using the the suggested API test kit the color indicated being somewhere between 20 to 40 ppm. The Pinpoint nitrate monitor showed 29 ppm.


0 days 01 hours

The sulphur denitrator ran for 1 hour with the effluent valve wide open to allow the water to circulate through the unit. The effluent water then tested to be 25 ppm. This documents an immediate 4 ppm decrease in the first hour. alt

Here is a picture showing the denitrator effluent.


After running for one hour wide open, the effluent was set as slow as i could get it. Roughly 40-60 drips a minute.

0 days 02 hours

A test of the effluent 2 hours into the cycling shows an immediate drop of 2 ppm.


0 days 03 hours

A test of the effluent 3 hours into the cycling shows a remarkable drop of 7 ppm. As seen below the effluent is now testing 16 ppm.


0 days 04 hours

A test of the effluent 4 hours into the cycling shows no decrease in nitrates from the effluent.

0 days 05 hours

At the 5th hour the effluent test to be 12 ppm. That is a 17 ppm drop in the effluent in as little as 5 hours.


0 days 06 hours

A test of the effluent 6 hours into the cycling shows the effluent creeping back up to 16. The increase is normal and indicates that the drip rate will need to be raised shortly.


A test on the tank water shows the nitrates have dropped from 29 ppm to 24 ppm.

0 days 16 hours

Overnight the nitrates rose to 18 ppm. The drip rate will now be double to 80 drops a min.


0 days 17 hours

The effluent was tested again, 1 hour after the flow rate was increased (doubled). The nitrates are back up to 22 ppm.


The tank water was also tested after the effluent was doubled to 80 drips a minute showing the nitrates have climbed to 26 ppm. This seems to be working backwards, since the nitrates have climbed. This is part of the cycling procedure.


0 days 20 hours

A test 3 hours later showed the same readings.

1 days 3 hours

A test 7 hours later shows the nitrates in the effluent rose by 1 ppm to 23 ppm.

1 days 7 hours

A test 4 hours later shows the effluent starting to drop again to 20 ppm.


1 days 17 hours

Test show 10 hours later the effleunt has dropped to 10 ppm. The tank water was again tested showing the nitrates to be at 23 ppm.


2 days 8 hours

15 hours later the shows Lo on the Pinpoint nitrate monitor.


Now that the Pinpoint monitor is reading Lo it is time to recalibrate the monitor to the low side so that we can get accurate readings.

The drip rate was increased to 100 drips a minute while the Pinpoint monitor was being calibrated. After calibration the nitrate reading was 10 ppm.

At this time the effluent was again raised to 120 drips per min.

2 days 7 hours

Effluent test show the nitrate level to be 2ppm.


2 days 7 hours

The effluent was increased to a “weak” stream.

2 days 14 hours

Test on the effluent show the nitrate level is now untestable by the Pinpoint monitor.


Test on the tank water also show the nitrate level to be untestable.

Now that the tank has been reduced to virtually no nitrates the effluent will be increased to a regular stream as the filter will need to turn over more water. If the effluent is not increased enough a rotten egg smell will be noticed. If this is experienced, simply increase the flow slightly.



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One Response to “Sulphur Denitrator Break in / Cycling – Step By Step”

  1. bychance says:

    I use one and love it!

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