Poor Man's Nutrients Control - Donovan's Nitrate Destroyer

Steve2020

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I just emptied each side of the DND. What I found was the aerobic side had a lot of whitish light tan slime but only about the first 8-12 inches and very light accumulation of slime the rest of the length of the tube. The anaerobic side had a pinkish slime that was very thick in a few areas but mostly light throughout the whole tube. What surprised me is that it was the larger media that accumulated the majority of the slime. The smaller media including the ceramic rings had very little slime so it looks like the larger media is what was causing clogging.
So, any thoughts or recommendations on why this happened with the larger media and should I just use the smaller media? I actually layered the large and small media and I am thinking if I mix up the media instead of layering it that it may work better as far as clogging.
I have the media separated by sides in buckets with salt water as we speak.
Thoughts?
 
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Reeftank2008

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Hi Steve

I can't really comment on why however I have experienced a similar scenario tonight that I have a white build up on my outlet?

Does anyone know if this is a good thing or bad thing? I haven't got any smell but I'm unsure if this means the flow is to slow however testing the nitrate I still have 10 nitrate coming out the DND?

If the slime is bacteria shouldn't the reading be zero? Or am I dosing too much carbon causing the bacteria slime?

Pic for reference.

Thanks Craig
IMG-20220930-WA0010.jpeg
 

Steve2020

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Hi Steve

I can't really comment on why however I have experienced a similar scenario tonight that I have a white build up on my outlet?

Does anyone know if this is a good thing or bad thing? I haven't got any smell but I'm unsure if this means the flow is to slow however testing the nitrate I still have 10 nitrate coming out the DND?

If the slime is bacteria shouldn't the reading be zero? Or am I dosing too much carbon causing the bacteria slime?

Pic for reference.

Thanks Craig
IMG-20220930-WA0010.jpeg
I rinsed all my media in salt water and put it back in the DND a little differently. From what I have read about carbon dosing is that the slime is a byproduct of the bacteria feeding on the carbon. When I used to carbon dose my tank I would get the pink slime in my filter socks but not at the amount I found in the DND. I am going to reduce my carbon dosing to the DND, about half of the recommended amount. Also may increase my flow rate to 2gals per hr vice 1gal per hour. That will still give me 2hrs from the time the water enters and exits the DND. Time will tell if this works for me.
 

Steve2020

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So do you increase the flow once that white bacteria is seen kn the outlet or do you decrease the carbk dose?
Myself I would reduce the carbon dose but then again I am no expert at this. Maybe someone else that has had a functioning DVD for awhile can respond. Bacteria needs a carbon source to thrive and reproduce. I am just not 100% sure how much carbon is actually required. I think there is a balancing act with carbon dosing and flow with these systems. Too much carbon and or to much flow will put the carbon source in your aquarium which you may or may not want. Not enough carbon and or to much flow will not allow the bacteria to thrive. Too much flow will not allow the Anaerobic Bacteria to consume all the NO3. Not enough flow may produce Hydrogen Sulfide. I am sure there are a few other scenario's but it is obvious to me that it is a balancing act and finding that proper balance may take some time. I ran into the worse case to where I had extreme clogging to the point that my emergency overflow kicked in. This required me to clean all the media in salt water so I wouldn't lose my entire bacteria population. I am not looking for an immediate lowering of NO3 so my plan is to dose less carbon and increase flow. My tank NO3 has come down to 11.3ppm which is fine for my tank but I want to get it to 5-7ppm and maintain that level. My tank is mostly LPS and only have 5 Acro's. LPS are doing great and 1 of the 5 Acros ( Tort ) is growing like crazy but the the other 4 look fine but just not growing like I believe they should be and very little polyp extension but they are encrusting a little. I want to get many more Acro's but want to get my NO3 and PO4 down a little bit more.
 

Reeftank2008

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I've noticed this morning that the slime has built up again but my understanding is according to DOnovan that the slime is good as its showing the reactor is working. I agree you need flow and it is a balance but you can't increase flow whilst you are still having a reading out of the reactor? It's only when this drops should the flow be increased to a maximum of 10% of the tanks turnover. It is then the carbon reduction starts to hold your nitrates stable. I could be wrong but that's what I thought lol.
 
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olonmv

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Been real busy at work so I’m just gonna mention real quick. Somewhere Donovan mentions the slime. His suggestion was to ride it out without carbon dosing and regular flow for a few days in order for the slime to subside. That slime, if I’m correct is a bunch of bacteria and is what we’re after in a controlled environment.
 

CNDReef

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Dosing carbon to the reactor is assuming your carbon deficient in the tank water. If there’s enough carbon already in your tank and you dose more carbon, it’s like overdosing vodka to the tank. Once you get a effluent of 0 No3 you should also start reducing your carbon source. Like said previously it’s a big balancing act that will differ between every DND. If I set one up again I will try to keep it at just under 1 ppm no3 effluent so I can see if i need to increase or decrease anything as time goes on.
 

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So today I tested the nitrate in the tank and nitrate kn the outlet of the DND. I have the same reading kn both with the flow kn the stepper pump running at 35ml per min. So I'm turning over 10% of the tank. The nitrate level is between 5-10ppm on both. I am going to leave everything as it is for now to see if the nitrate drops on the outlet some more, if it does I will back off the amount of carbon....
 
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Steve2020

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As I reported this past Friday I had to empty out my DND and clean all the media in fresh saltwater due to extreme clogging in the DND. It took about 2 hours of rinsing because I have a lot of media in my unit. My concern after putting the DND back in service was that I was going to lose a lot of bacteria and have to start all over but that seems to be not the case. I reduced the carbon dose amount from 18ml spread throughout the day to only dosing 2ml every 6hrs for a total of 8ml/day. I also have increased my flow from 60ml/min ( 10% ) to 100ml/min ( 15% ) and today this is my effluent reading as shown in the photo. I will need to increase my flow rate and or reduce the carbon even more due to I am approaching my tank target NO3 goal of 5-7ppm. Tank NO3 today is 9.1ppm with the HR Hanna Checker.
So the moral of the story is if you have clogging to the point discharge flow stops, If you clean your media properly you should not lose the bacteria population to the point of having to start over. Just a FYI.
20221005_083128.jpg
 
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olonmv

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If I remember correctly you are running a pressurized single tube DND. Don't quote me on this but it is a good thing not to have the rotten egg smell ( hydrogen sulfide ) and as far as nitrogen gas, I do not believe you will see the gas bubbles like in my system because the nitrogen gas is dissolved in the water and with no void space in your system the gas will not be removed from the water until it exits the DND. If the denitrification process is happening in your DND which it seems it is then you are producing nitrogen gas IMO.
As far as carbon source in your tank from the DND, to me that would mean you are dosing to much and the bacteria is not consuming most/all of it.
I am no expert at this to say the least so hopefully someone else will chime in with their opinion if they find my explanation incorrect.
You’re correct, single tube pressurized DND. What you say makes complete sense. Completely sealed and the outlet of DND points upward so no gasses get trapped in the DND. I haven’t had much time to tweak my DND (am on like day 40 with no days off and hopefully one to come this weekend). As for the cyano…..it’s till there. Last night my tank nitrates were at 11.5 ppm (missed a couple-few dose days and it shot up to 18ppm). I’m sure I need to reintroduce my filter on the effluent side as I’ve been regularly siphoning out small amounts of slime from my DT. If I don’t work this weekend I plan on opening up DND to see what’s goin on inside and to introduce the seachem matrix I bought a few weeks backs. Rarely do I check effluent side of DND….just FYI. I Will keep y’all posted.

also, currently dosing cipro in my tank because I have a sick nem. The good thing is, a while back I decided this was gonna be my experimentation tank so I’m willing to try off wall treatments, hence the in tank Cipro treatment.
 
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olonmv

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Is it safe to stop the flow thru the DND for an hour or two? I want to clean my Vectra M2, L2 and sump today. Don't want to build up any Hydrogen Sulfide in the DND.
It’s mentioned that if you stop the DND for an extended amount of time (a day or more), to just drain about 1/2 hours worth of DND water. 2 hours shouldn’t be too much of a problem though.
 

olonmv

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Sooooo, tomorrow marks 2 months since I started my (mini) DND. In case you’re not up to date, I’m running a really small DND that is a completely sealed system which is mounted under my tank. I have no sump and run an evo 13.5 AIO tank. The media in my DND is singular as in I’ve only used one type of media similar to this, Aquapapa Aquarium Biological Bacteria House Ceramic Rings Filter Media 6 lbs Bagged for Pond Fish Tank Canister Filter https://a.co/d/i5wkBF8. I also had planned on using a couple of 1/2 layers of seachem matrix but my dumb butt ordered the activated carbon by accident so I just rolled with the one media type. Sized my DND based on my tank volume in gallons multiplied by .027. That gave me the DND size I needed for my size tank. After I cleaned the media in RO I loaded up my DND with the media. I followed the recommended dosage and flow rate based on my DND/tank size. I was doing 1ml straight 80 proof vodka once a day and flowed to about 3.5ml a minute (literally drops no stream) for the better of the 2 months. Easiest way I found to tune my DND’s flow rate was with a metronome. My flow was set to 47bpm (or drops per minute) which would fill my measuring tube to 3.5ml per minute once I figured my “dpm” I just pulled up my garage band app up and used the metronome on the app (just realized Google had a metronome you can use straight off the interweb). my flow is provided via a pond pump that I modified to work with tubing which is housed in my first chamber under my filter floss. I adjust my flow with valves that are inline to my pump. Flow has to be adjusted daily and sometimes a few times a day, don’t get discouraged with this….it’s worth sticking with it. Started this venture with 36ppm and I’m finally down to 6.6 as of yesterday. It was lower but I’m in the process of learning what my daily dosage should be to keep my at about 5ppm steady. I’ve reduced my carbon dose from 1ml to .25ml and I suspect that my daily dosage will be in the .20ml range. That should keep up with my feeding habits. Anywho, hope this helps anyone who’s interested in making one for their Nano. Kept reading how difficult it would be to make one for a nano with no sump, well…….IMO it really wasn’t too bad and it CAN be done.
 

olonmv

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Not saying this does not work but why not just use a sulfur media bed? To me it seams simpler. Low flow through a single media done.
I personally went this route because my tank was already established when I stumbled onto this thread. But, honestly. I’m thinking of going this route when I decide to pull the trigger on a bigger tank. It’s a super easy reactor to make and it’s external of your tank. I can very easily take my DND off-line with just a couple of closures of valves without even a drop of water loss and, if I had to make adjustments to the DND Nothing gets disturbed in the tank. Perhaps one day I’ll read something that drifts me towards sulfur media bed as I’ve read great things about them but for now…..this was kinda way too easy and I already have an understanding of it.
 
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olonmv

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Has anyone tried cycling one in a bucket of tank water? Also how do you introduce the carbon via a doser with getting water pushed up the dosing tube?
You can seed in a bucket, and I’d imagine a one-way valve would take care of back-feed issue.
 

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