Guide to DIY De-nitrator

I have noticed that some bros still have many queries about how to go about doing a diy de-nitrator therefore I decided to post this little "article" I have written. It compiles all information in all my previous related thread and also all questions through PM or in the forum that I was answering to. Hope this could help bros who might be interested to know some basic procedures in diy-ing their very own de-nitrator. This "article" serves only as a general guide to help those who need it. It’s not to assume that I’m totally correct as this article only sort of consolidate some things I have learnt from very experienced bros here, through my readings and personal experiences. This article is also not debating on the best method to remove nitrate. Of course there are many other mechanical and chemical or even natural ways, which are sweared by some bros here who has experience using them. This article is more for bro who has done some researched and decided to diy their own coil de-nitrator, to help them to accomplish in their forthcoming diy project. I have included whatever that I know in this post so those new bros don’t have to search through the whole list of old threads jus to gets bits and pieces of loose info. This is going to be a long read but I think it will definitely benefit many. I have included the general guide, the science behind cycling and some extra info, which you might be interested if you are building one yourself.

The Science behind the cycling process: "Nitrogen Cycle"

If you are reading this article, congratulations! It means that you already understood what the entire nitrogen process is about. That’s why you are finding ways to remove the toxic nitrate if accumulated in high level without water change. Ammonia (toxic) will need to be broken down to nitrite (toxic), which needs to be broken down further into nitrate (ok level of toxic for fish). I can safely and proudly assume that bros here already have tip top water management in terms of zero NH3/4 and NO2. Give yourself a pat on your shoulder. Now we are all looking for more advance stage of water management. That is how to further break down NO3 (nitrate), which is a by-product of NO2 breakdown process, into nitrogen gas and to be escaped through the tank water surface.

My diy is based on a few assumptions/facts:

1. Anaerobic bacteria can only be cultivated in oxygen free environment.
2. Oxygen riched water passing thru a 20m 1/4" tube at drip rate will emerged with oxygen free water. This is due to the aerobic bacteria along the inner tubing consume all the oxygen. By the way, its this aerobic bacteria commonly found in our filter media that break down your NH3/4 to NO2 to NO3. Hence we have accumulation of NO3, which will be toxic. They can be removed through water change. Some find it too expensive to do constant large amount of water change for their huge tanks. Even our tap water has certain amount of NO3. Therefore we are looking for method to cultivate the anaerobic bacteria to tackle the high NO3 problem. Thus reducing the need of large constant water change.
3. Anaerobic bacteria hosted on the bioballs will convert the nitrate to nitrogen.

Material require to build the coil de-nitrator

$3 for 25m air tube, $8 for 2.5ft 4" pipe, $6 for 2 4" end caps, $1 for air tube connectors and valve, $2 for super pvc glue. 100+ bioballs from ios tank. Input pump is tapped on to the air hose of 1400l/h powerhead in the main tank meant for water current (tat means I dun need extra powerhead to drive the de-nitrator and incur more electric bill). Silver spray paint left over from my previous tank cabinet work project.

Steps on building it

1. It’s not easy to coil the air tube neatly by the side of the inner pvc pipe. So I just coil it round my hand. Make sure no acute bend and slowly push the bundles into the pvc pipe. Having done that. I’ll have one end of the air tube at the bottom of the pvc pipe and the other end extend up to the top of the pvc pipe.
2. I’ll use the suction cup that is used to hold the tank partition and stick it on one of the end cap. Then I’ll position the end of the air tube at the bottom of the pvc pipe onto the partition holder. This is make sure that the water outlet from the air tube will be positioned at the center of the bottom pvc pipe.
3. Cover up the end cap at the bottom of the pvc pipe. Seal up the end cap with the pvc glue.
4. Temporary cover the top end cap. Wrap the top end cap with newspaper and masking tape. Spray paint the entire pvc pipe including the bottom sealed end cap.
5. Drilled 2 small holes on the top end cap sufficient to tightly squeeze through the 2 air tube connectors.
6. Insert the 2 air tube connectors into the holes and seal them up with pvc glue.
7. Connect the top end of the coiled air tube in the pvc pipe to one of the connector at the top end cap.
8. Fill up the pvc pipe with bioballs.
9. Top up the de-nitrator with tank water.
10. Cover the top end cap and seal with pvc glue.
11. Remove or break the air inlet connector of the submersible powerhead and insert a segment of a new air tube into it. This is to pump the water from the tank into the de-nitrator. The air tube needs to be inserted through the air inlet of the powerhead and position all the way towards to motor. In this case, while water is pump out fro the powerhead outlet, at the same time it will also be pushed though the air tube into the de-nitrator.
12. Switch on the powerhead. Water will flow through the coil air tube in the de-nitrator and flow out from the bottom of the pvc pipe. Water and pressure will build up in the de-nitrator. The other free end of the air tube connector at the top end cap will automatically push the water out by pressure.
13. Connect an air tube to the outlet of the de-nitrator and the other end of the air tube connects to an air valve. This is use to control the water flow rate later on.
14. Now your de-nitrator is working. Congratulation! However that’s only the mechanical portion.
15. In order to kick-start the anaerobic bacteria, we need to feed the bacteria in the de-nitrator with sugar. Cut the inlet air tube between the powerhead and the de-nitrator inlet valve. Put in some fine sugar in the air tube. Connect back the air tube with a connector for future feeding if necessary.
16. Adjust the air valve at the outlet air tube and let the water flow at a rate of one drop per second.
17. We are done here!