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DIY Denitrator


cpfc
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I saw Craig's denitrator on his 2000l tank. I am getting nitrates between 10 to 30 which is fine for the moment but leaves no room for error. I saw a jar of dentritator which got my brain thinking. From what I can tell a very low flow is needed. I was thinking of using a section of PVC to hold the media. That is the easy bit.

Next part is power. I was thinking of using either gravity off the overhead or a feed off the cannister.

Anyone else here setup a denitrator who could point me in the right direction?

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Glad you were inspired :yes: Here's somthing from an old post about my "canister" denitrate filters Vs. coil;

The anaerobic bacteria that break down nitrate require the same "essential" living requirements as the aerobic bacteria that break down ammonia and nitrite.

Except they require and environment that is devoid of oxygen.

Aerobic bacteria require;

1 surface area (to live on)

2 oxygenated area

3 water flow to bring food supply (and O2)

4 food (ammonia and nitrite)

Anaerobic bacteria require;

1 surface area (to live on)

2 NO oxygen area

3 water flow to bring food supply (with no O2)

4 food (nitrate)

Limit 1, 2 or 3 for aerobic or anaerobic bacteria and you create a limitation to their population levels which in turn limit their beneficial effects.

The trick with anaerobic bacteria is to provide an anaerobic zone where they can live happily and their living requirement (i.e. no oxygen) will not have any negative impacts on the aerobic area where our fish live.

This is is easily done by creating an extra "filtration" area which has limited water flow (to limit the O2 penetration) and is cut off from oxygen. By limited water flow I mean limited only in comparison to the greater water flow expected with a standard aerobic filtration. With an anaerobic filter, as with an aerobic filter, if you limit the water flow you limit the amount of food for the bacteria. In the case of anaerobic bacteria you want as fast a water flow as will still maintain an anaerobic area, less than this maximum flow and you will limit the food transportation system (the water flow). It is contrary to common sense to use a denitrate reduction system that by design has VERY limited water flow such as with coil denitrate filter.

You can make your own canister with PVC plumbing fittings (I have made several out of 150mm fittings and pipe), put some bulkhead fittings on it to allow water in and out, fill it with Seachem Denitrate media, then limit the water flow to a max of 20 gallons per hour (20 gallon/hour [uS] = 75.708 235 677 liter/hour = 76 lph). I personally prefer to limit the water flow to less than the maximum recommended but at even half the maximum flow (at say 38lph), water will be gushing out compared to the maximum dripping rate produced by a "coil denitrate" filter.

You can also get an old canister and provide an external pump. An old style Eheim filter where the motors are sitting on the lid instead of incorporate in it is ideal for this. If the pumps flow rate is too great you can "T" junction off the excess water flow to maintain a limited water flow through the anaerobic zone itself. I have always used the smallest Eheim Hobby pumps.

The other advantage of a canister filled biological denitrate filter apart from the increased output due to greater water flow, is that it has a MASSIVE surface area compared to the very limited "one" surface area provided by the internal surface of the coil in a coil denitrate filter itself.

There really is no comparison, when comparing the effectiveness of a coil denitrate filter with an enclosed "canister" style filled with a biological media. The canister style wins not only with the amount of water process but also the available living space.

Edited by CThompson
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Items needed look like

Section of PVC pipe with correct volume to hold the denitrate.

Bulkheads for pipe - Is this available at bunnings or Reece? Do they have connectors for the inlet/outlet pipe or does that have to be drilled?

Pump - low flow <75lph - Will have to look for this? Anyone have a good pointer?

Pipe glue

Tubing to connect to tank - What diameter?

Another denitrator I saw was in an overhead filter with the media underneath a sandbed. Sounds easier to setup but the sand brings in its own issues.

]Glad you were inspired :yes: Here's somthing from an old post about my "canister" denitrate filters Vs. coil;

You can make your own canister with PVC plumbing fittings (I have made several out of 150mm fittings and pipe), put some bulkhead fittings on it to allow water in and out, fill it with Seachem Denitrate media, then limit the water flow to a max of 20 gallons per hour (20 gallon/hour [uS] = 75.708 235 677 liter/hour = 76 lph). I personally prefer to limit the water flow to less than the maximum recommended but at even half the maximum flow (at say 38lph), water will be gushing out compared to the maximum dripping rate produced by a "coil denitrate" filter.

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Personally I don't see the logic of denitrate filters in freshwater tanks.... :B

but Happy to be educated.... :yes:

With freshwater tanks nitrate control is best handled by

Water changes

or

Use duckweed to remove nitrate ?

perhaps another tank with lighting? or even duckweed in the sump?

Then....if a mbuna tank....duckweed can be used for food!

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I have a lot of val in there which I was hoping would do a similiar thing. Makes a good refuge for fish. Main logic for me is to ensure maximum water quality and see how effective it is. Basically educating myself. The other part is if for whatever reason I have to be away a weekend I can be rest assured nitrates are not going to be an issue.

I would love to do another tank hooked up and filled with plants. I could dump fry in there or put in a mesh that stops the big fish getting across. No space at the moment though.

I am new to all this so it will be self education with some experimentation.

Personally I don't see the logic of denitrate filters in freshwater tanks.... :B

but Happy to be educated.... :yes:

With freshwater tanks nitrate control is best handled by

Water changes

or

Use duckweed to remove nitrate ?

perhaps another tank with lighting? or even duckweed in the sump?

Then....if a mbuna tank....duckweed can be used for food!

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Personally I don't see the logic of denitrate filters in freshwater tanks.... :B

but Happy to be educated.... :yes:

With freshwater tanks nitrate control is best handled by

Water changes

or

Use duckweed to remove nitrate ?

perhaps another tank with lighting? or even duckweed in the sump?

Then....if a mbuna tank....duckweed can be used for food!

Denitrate filters do not replace a water change. They simply keep the nitrate levels at a lower level than they would otherwise be, with or without a water change.

Will you notice a difference in the fish? Nope.

Will the water have a lower nitrate reading? Yep.

Is a lower nitrate a good thing? It certainly is not bad.

Duckweed and other plants use nitrate as a fertiliser. My old planted tank with CO2 injection, I actually had to add and increase the nitrate levels because they had become a limiting factor.

It will, I expect be, a bit of a personal choice as to whether you use a green nitrate reduction or biological nitrate reduction system. A personal choice born about to a large degree due to circumstances.

Having plants in an African tank, though possible, is adding another layer of maintenance, and can be problematic. You might prefer this look, but you will need a LOT of plants to impact on nitrate levels. Having a separate but plumbed in tank where the greenery can go and be separate from the fish, is a great alternative, but you need the space. And it will take a lot more room and continued effort that a denitrate filter tucked away in a dark corner under the tank.

Personally, in a display tank I would not add duckweed as it is messy, it blocks the light, and can be difficult to eradicate should you change your mind. All it takes is one piece missed and it’ll all grow back.

If mbuna (or other fish) use duckweed as a food, then it will not be possible to sustain meaningful amounts to reduce nitrate levels, and will not be an option anyway.

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I am thinking of utilising the existing 1000lph powerhead that sends water into the overhead filter. The idea is to put a valve in there and send off some water to the denitrator. Next part is where do you get these valves? Recommendations, tips or things to avoid.

Another option is running it off the outlet of the cannister with a valve so only some of the flow gloes through the denitrator, the water is deoxygenated from the cannisters bacteria and already filtered to minimise clogging. The wife will think I have lost it and my son will love it.

Apparently another advantage of low nitrate is a more stable pH and KH.

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Another option is running it off the outlet of the cannister with a valve so only some of the flow gloes through the denitrator, the water is deoxygenated from the cannisters bacteria and already filtered to minimise clogging. The wife will think I have lost it and my son will love it.

I would go with this option for the reason you mention+

  • it will be easier to control flow.

  • An in-line flow meter from filter to denitrate filter would be step in the right direction too. That way, as the filter dirties, you can see the flow rate fall to the denitrate filter, and use this as a guide when to clean filter.

  • Water going too the denitrate filter should be filtered BEFORE it gets to it. On my 800 l mbuna tank, it is filtered three times before getting to the denitrate filter.
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No pump needed

2 bulkheads - Anyone know a good source?

PVC Pipe- hardware store

Valve to divert some flow from cannister - Anyone know a good source?

Pipe from valve to denitrator -

Return from denitrator to tank

pre and post denitrate sponge to hold media in place

Flow meter (optional) - Anyone know a good source?

I would go with this option for the reason you mention+

  • it will be easier to control flow.

  • An in-line flow meter from filter to denitrate filter would be step in the right direction too. That way, as the filter dirties, you can see the flow rate fall to the denitrate filter, and use this as a guide when to clean filter.
  • Water going too the denitrate filter should be filtered BEFORE it gets to it. On my 800 l mbuna tank, it is filtered three times before getting to the denitrate filter.
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No bulkheads but I think I have the parts.

The poly fitting stuff for irrigation is the go. I have a section of 100mm pipe, a cap and a head with a screw on cap.

I have a valve and various poly fitting parts including a T to tap off flow from the cannister. A section of egg crate with sponge above with go at the bottom of the "cannister" which will support the denitrate. I got the bits from Bunnings and Gainforts in the area. The two sections in Bunnings are the irrigation and the water tank section.

Maybe later this week I will silicone it together. My 4 year old is obsessed with plumbing and is loving it and the excess pipes.

The parts cost less than the denitrate and I cannot believe the price of the commercial denitrators.

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A section of egg crate with sponge above with go at the bottom of the "cannister" which will support the denitrate.

You will be better off using a "predator mesh" (like a finer gutter guard) than a sponge. Dependant on what you mean by sponge, and how fine it is, it will be prone to blocking up to easily. As a first point of contact, if it blocks the whole thing will stop.

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It is a course sponge.

Do you know where you can get flowmeters?

A section of egg crate with sponge above with go at the bottom of the "cannister" which will support the denitrate.

You will be better off using a "predator mesh" (like a finer gutter guard) than a sponge. Dependant on what you mean by sponge, and how fine it is, it will be prone to blocking up to easily. As a first point of contact, if it blocks the whole thing will stop.

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It is a course sponge.

Do you know where you can get flowmeters?

A section of egg crate with sponge above with go at the bottom of the "cannister" which will support the denitrate.

You will be better off using a "predator mesh" (like a finer gutter guard) than a sponge. Dependant on what you mean by sponge, and how fine it is, it will be prone to blocking up to easily. As a first point of contact, if it blocks the whole thing will stop.

It will need to be a VERY course sponge, and without seeing it, would still be more inclined to go with a single sheet of plastic mesh (not flyscreen). A sponge can pick up matter and potentially block.

Try contacting Aquasonic, I think they have them, but I'm not sure. If they do they can point you to a lfs, or the lfs can get them in for you.

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Hey,

Love a good DIY post...

I was also inspired to make a DIY filter like Craigs around the time I was getting into the hobby, but it was only a half-hearted attempt to maintain it as I was busy with other things at the time. I now have some new found time on my hands and want to make another in a few months.

I think there used to be a DIY article on the forums somewhere for Craigs DIY Denitrator but cant seem to find it. Any ideas on where it got to? or am i dreaming?

I was thinking of doing something similar to what cpfc is describing.

I have a system that holds around 2500L of water.

I have found a few articles online for DIY PVC sulphur denitrator filters mainly used for marine setups. They use PVC pipe standing end on end about 3-4feet high.

Cant seem to find the actual article I was reading previously, but it is similar design to this one ---> DIY Fluidised Bed Filter

I have a few questions.

- Would a few of these filters running side by side be more effective for reducing nitrates given I have a large amount of water in my system? If I remember correctly, CThompson, you have a smallish DIY unit running on your large setup that is about 2000L.

- Would the system also work to reduce nitrates if it were using sulphur beads? or does this only work for marine systems? I can only seem to find articles relating to marine systems...

- Would it also work to reduce nitrates if some of the PVC canisters were run with media other than denitrate? eg. sand to be run like a FBF? The canister should still provide the 'Anaerobic bacteria requirements' listed previously - right?

- Most DIY denitrate filters I have found have a gasket (usually made of acrylic) on top. Is there a specific reason for this? Can I just cap the PVC with an end piece, which is what i thought CThompson has done on his?

Thanks

cfpc:

Sorry to butt in on your post but I thought it could also be useful to you and others.

I would probably steer clear of fly screen unless you have prefilter somewhere before the water gets to it. I think it would clog way too easily otherwise. Would a few sponge filters in the pump compartment of your sump help to get rid of any debris in the water column before it gets to the pump and then on to the denitrate filter?

Interested to see how yours goes. Keep us informed.

Goodluck :thumb

Cheers

Joel

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Hi Joel. Hopefully this weekend I will have time to stick some of it together. The more input and ideas from anyone the better. I am capping mine with a screw piece so I can access it. The water going into the filter will already have been through a cannister with wool, sponge, matrix and noodles.

A question I have is if I open the denitrator will I kill the active bacteria.

Another question is will this stuff exhaust and does anyone know a ball park.

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- Would a few of these filters running side by side be more effective for reducing nitrates given I have a large amount of water in my system? If I remember correctly, CThompson, you have a smallish DIY unit running on your large setup that is about 2000L.

You don't mention how much water. Remember, the nitrate is not that big a deal, are multiple denitrate set ups worth the effort? If you think so, why not make one long one, 110mm pipe comes in long lengths :dntknw:

I consider it to be a fairly large denitrate chamber on my tank.

- Would the system also work to reduce nitrates if it were using sulphur beads? or does this only work for marine systems? I can only seem to find articles relating to marine systems...

Don't know this product.

- Would it also work to reduce nitrates if some of the PVC canisters were run with media other than denitrate? eg. sand to be run like a FBF? The canister should still provide the 'Anaerobic bacteria requirements' listed previously - right?

If you can maintain an aneorobic water flow.

- Most DIY denitrate filters I have found have a gasket (usually made of acrylic) on top. Is there a specific reason for this? Can I just cap the PVC with an end piece, which is what i thought CThompson has done on his?

I seal all entry points bar one, which I close with an O-ringed screw on lid for future access if needed.

Edited by CThompson
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Thanks for that.

You don't mention how much water. Remember, the nitrate is not that big a deal, are multiple denitrate set ups worth the effort? If you think so, why not make one long one, 110mm pipe comes in long lengths

My system is 2500L spread accross 12 tanks. I dont think it is a major deal, but at the moment the only denitrifying works are in the substrate of sand in the tanks. I think it will be worth the effort to reduce nitrates or even to satisfy myself that i tried.

I was thinking of making a few 110mm by about 1000mm high or whatever height dimension best fits underneath my rack. There would be maybe three in a row, where the water would travel from one canister to the next and then to the sump. Is this overkill? Im thinking the more surface area the better and as the water flows through each of the canisters it will be further stripped of any oxygen in the water to maintain an anearobic rich environment.

I have found the article for a DIY Sulphur denitrator similar to what I want to make. The article is a summary of a longer discussion on another forum. There is a link within it if anyone is interested to read the extended discussion (it is a hefty read :shock: ). see here ---> DIY Sulphur Reactor

Don't know this product.

I am referring to these --> Sulphur beads

But I think it should still work just as well without this specific media.

I seal all entry points bar one, which I close with an O-ringed screw on lid for future access if needed.

I thought that may have been the case. Since you have had yours up and running have you ever opened it to do any maintenance? I realise that it would then have to be re-cultured with anearobic bacteria afterwards which takes some time.

Thanks!

The water going into the filter will already have been through a cannister with wool, sponge, matrix and noodles.

I see. I would still probably aim for something that would be almost impossible to clog up. I know fly screen is cheap and easy to get a hold of but you dont want to keep stopping the system to clean it out as it takes a while to restart the denitrifying bacteria again.

Joel

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but at the moment the only denitrifying works are in the substrate of sand in the tanks

You won’t have it here, if you do, you will see methane bubble, or black sand or some other activity you don’t want in a fish tank.

I think it will be worth the effort to reduce nitrates or even to satisfy myself that i tried.

Couldn’t agree more.

I was thinking of making a few 110mm by about 1000mm high or whatever height dimension best fits underneath my rack. There would be maybe three in a row, where the water would travel from one canister to the next and then to the sump. Is this overkill? Im thinking the more surface area the better and as the water flows through each of the canisters it will be further stripped of any oxygen in the water to maintain an anaerobic rich environment

Filled with SeaChem Denitrate, you will have a HUGE surface area with something half a meter high, and though I couldn’t give you a solid reason for my opinion, I think you will find one denitrate filter 500 mm would be okay on its own. SeaChem Denitrate is going to have a $ factor as well, so the more filters you make, the more it will cost to fill and probably the less bang for your buck will be had.

It has been my working understanding that the first few centimetres (dependant on flow rate) inside the column will potentially have excess O2 to prevent anaerobic bacteria. If that is the case then it will be colonised by aerobic bacteria = stripped of O2. After this point, the size of which will be influenced by water flow, it will be anaerobic and stay that way for the rest of the chamber.

I thought that may have been the case. Since you have had yours up and running have you ever opened it to do any maintenance? I realise that it would then have to be re-cultured with anaerobic bacteria afterwards which takes some time.

The way I finished up designing my dentrate filters was to use a 110mm “T” piece on its side (so it can stand with the short side horizontal with the floor). The plumbing goes through the side, and once in the middle of the chamber, a right angle takes the pipe to the bottom of the chamber. I screen off a clear section at the bottom with predator mesh, held off the floor with a few 10-20mm narrow pieces of pvc. This allows the water to flow the full length of the chamber before exiting, with a similar predator mesh system at the top.

Over the years I have not opened it/them, but that doesn’t mean I shouldn’t.

I would suggest you make one denitrate filter, and put all the rest of your enthusiasm into making sure the water that gets to the denitrate chamber is so clean the filter will never get dirty. You'ld be surprised at how difficult this is.

Upon further consideration, your previous question regarding the use of sand instead of the SeaChem media, and run it like a FBF, I don’t think will work. Any flow that is strong enough to lift all the particles into motion in say a 500 mm long 110 mm sized pipe will be too strong to maintain an anaerobic zone as described above.

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You won’t have it here, if you do, you will see methane bubble, or black sand or some other activity you don’t want in a fish tank.

Oh. I do get air bubbles trapped in the sand sometimes. I thought this was the natural process of converting Nitrate to nitrogen. I rake the sand every now and then... I assume if I reduce the amount of sand it will help prevent this happening?

I would suggest you make one denitrate filter, and put all the rest of your enthusiasm into making sure the water that gets to the denitrate chamber is so clean the filter will never get dirty. You'ld be surprised at how difficult this is.

Thats probably a wise idea. I havent put much consideration into the pre-filter just yet.

Upon further consideration, your previous question regarding the use of sand instead of the SeaChem media, and run it like a FBF, I don’t think will work. Any flow that is strong enough to lift all the particles into motion in say a 500 mm long 110 mm sized pipe will be too strong to maintain an anaerobic zone as described above.

I was originally thinking that the amount of anaerobic volume within all of the cannisters would compensate for the higher flow. ie it would still be stripped of oxygen as it moved through to the later canisters. But I will save that until I get an itch to make a DIY Fluidised Bed Filter :lol1:

Ok. Thanks for the advise. :thumb I will start small with one and see how I go with that.

Thanks again

Joel

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Oh. I do get air bubbles trapped in the sand sometimes. I thought this was the natural process of converting Nitrate to nitrogen. I rake the sand every now and then... I assume if I reduce the amount of sand it will help prevent this happening?

you absolutely don't want this to happen. reduce sand level as you suggest.

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  • 3 weeks later...
Hi Joel

I have siliconed it together but am struggling to find a suitable mesh to support the denitrate.

Hi cpfc,

Are there any updates on this?

Cheers

Assuming you have used PVC pipes, you don't use silicon. Use plumbers glue.

Use egg crate for the mesh, perspex places usually carry it.

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