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

[McPuff]

Quick question, what do you use to separate the different sized media, or you don’t. Thanks

I would be really careful about using anything smaller than 1" in size or you will likely have issues with clogging.

 

[McPuff]

Quick update on my DND which [i just looked] I set up back in early July of 2025. My nitrates were over 200 at that time. Just did a quick test yesterday and nitrates could be as low as 10 right now! Keep in mind that I am not doing water changes on a regular basis. Usually they are just to remove sediment from the sump but it's pretty infrequent. That is to say that the reactor has been working really well. I may even have to dial back the vinegar a bit so that I can maintain some level of NO3 as I don't want it to go too low (I was thinking that 20 would be ideal). We'll see what the lab analysis says in about a week.

Phosphates have also come down quite a bit though that is due to GFO. It's really hard to color match with the salifert kit (for both NO3 and PO4) but I believe it's somewhere around 0.5 which is also a massive reduction from 1.5 that I measured in December.

Coupled with the change in lights, I have seen a big difference in coral health and once again am seeing actual growth from SPS.

 

[blazn]

Quick update on my DND which [i just looked] I set up back in early July of 2025. My nitrates were over 200 at that time. Just did a quick test yesterday and nitrates could be as low as 10 right now! Keep in mind that I am not doing water changes on a regular basis. Usually they are just to remove sediment from the sump but it's pretty infrequent. That is to say that the reactor has been working really well. I may even have to dial back the vinegar a bit so that I can maintain some level of NO3 as I don't want it to go too low (I was thinking that 20 would be ideal). We'll see what the lab analysis says in about a week.

Phosphates have also come down quite a bit though that is due to GFO. It's really hard to color match with the salifert kit (for both NO3 and PO4) but I believe it's somewhere around 0.5 which is also a massive reduction from 1.5 that I measured in December.

Coupled with the change in lights, I have seen a big difference in coral health and once again am seeing actual growth from SPS.

Thank you for the update, as it just might be what convinces someone to make their own DND. Once you've got one in action and see the results, it is a must have!

 

[ryewalk84]

For those that have done these outside the sump, what am I searching for to ensure the inlet/outlet drains are sealed? What have others used?

 

[McPuff]

For those that have done these outside the sump, what am I searching for to ensure the inlet/outlet drains are sealed? What have others used?

You would need to have a different design to run it outside the sump. Completely gluing parts together would be a necessity... or at least using threaded caps. Would you run it pressurized or still try to make it gravity fed? I think you'll run into some different challenges but you gotta do what you gotta do.

Do you have a working model yet or just some sketches perhaps? We can chime in after seeing what you've got.

 

[ryewalk84]

I’ve collected and assembled my parts and I’m currently in the leak test phase. First tower has an in for tank water, in for carbon and an overflow for blockage. Second tower has the output. Pipes are 4 inch diameter and 32 inch tall.

 

[McPuff]

Looks good! You'll fit quite a lot of media in that thing. Mine holds about 8.5# of the 1" spherical media. Also 4" PVC but it's 24" tall... though I also have a 4" connector at the bottom which is also full of media.

Good luck and keep us posted!

 

[Curiousbranching]

I’ve collected and assembled my parts and I’m currently in the leak test phase. First tower has an in for tank water, in for carbon and an overflow for blockage. Second tower has the output. Pipes are 4 inch diameter and 32 inch tall.

You should change the position of the carbon feed line so that it is considerably higher than the water inlet line to Tower 1. The current position will definitely cause very frequent blockages.

 

[McPuff]

You should change the position of the carbon feed line so that it is considerably higher than the water inlet line to Tower 1. The current position will definitely cause very frequent blockages.

Agree. I put the inlets on the cap for my own as it gave even more height differential with the outlet. Definitely recommend this regardless of whether you're using gravity or pressurizing the reactor.

 

[McPuff]

Just got my ATI test results back and NO3 just measured at 2.67 !! That's actually lower than I would like so glad I caught a better number than what my salifert test can provide. I'm going to lower than daily dosing amount of vinegar and see if I can keep the NO3 around 10-15.

PO4 is down to 0.34 which is also a massive improvement. Gonna just have to keep an eye on it as I continue to use GFO to maintain. Would like to get to 0.1 and stay around that area but not gonna chase very hard.

 

[ryewalk84]

You should change the position of the carbon feed line so that it is considerably higher than the water inlet line to Tower 1. The current position will definitely cause very frequent blockages.

I set this up before I saw your message. So far I’ve been ok. I think it’s because I have the overflow so the water level can never reach the carbon inlet.

UPDATE-
I went online 9/29. I chose to throw a chunk of coral skeleton on the top of the first tube to seed the bacteria. From there I let the tank water run through. Tank nitrates were at 50ppm.

10/5 I did a test on the outlet and it was showing 50. Maybe slightly lower. I use the Salifert nitrate kit. Unfortunately I ran out of reagent and had to wait for another to arrive.

10/13 I am at 0 on the outlet and guessing 40 in the tank.

I will say I am struggling to keep the flow consistent. I decided to go gravity fed off my return line and either the valve is clogging or the bacteria is clogging the outlet. Annoying but hoping it’ll settle in at some point. I’m questioning if I should have gone 3/8” for the in and out to have flow a little more consistent. The overflow has been working well and as intended.

Either way, excited to watch these nitrates drop.

 

[McPuff]

It should stabilize at some point but may take a while. I had the same issue. BUT, make sure to keep an eye on the effluent at least every few days. I give it a flick every so often to jar loose the bacterial plugs (snot) that form. And I make sure to keep the feed line flowing freely by removing it, opening it up fully, then adjusting it back down and reinstalling. All of it takes a total of 35 seconds but keeps things operating nicely.

 

[afboundguy]

I just read this entire thread and am thinking about adding a DND to my setup but had some quick questions:

1 - could I use reborn media as a layer?

2 - I don't think I read this, but has anyone used PNSB to help seed the media along with the other forms of bottles bacteria?

3 - If I have a bunch of bioballs in my sump already and use those would it drastically speed up the process?

4 - what's the lowest starting NO3 rate anyone has used a DND on? Last time I tested NO3 it was in the 10-15ppm range but that was before I added a ton of fish and I am having some nuisance algae problems so even if I had a low reading I know it's deceiving.

My main goal of adding a DND would be so I could increase my bioload and feeding. I plan to have around 20-25 smaller fish in my 80/60 "drop-off" tank that has 195 gallons total with the sump and a 35 cube that will be a harem tank.

Right now I have 13 fish with 3 in QT that will be going in next weekend and would love it if the DND would allow me to go above 25 fish as the "drop-off" tank is 6 feet long by 2 feet wide so there is plenty of swimming room and they are connected by bulkheads so the fish can swim between each tank.

I've always wanted a bunch of smaller fish to have so much activity and I am planning my fish stocking so that each level of the tank is filled with fish!

Thanks in advance and it was a blast reading all 87 pages! Definitely helped me get through the absolute suckiness of work the past two days!

 

[McPuff]

That's a cool way to construct a drop-off tank. How frequent do you see fish movement between the tanks? And what's the water transfer rate like?

You can definitely set up a DND for your system but you may want to just get it seeded and let it settle in with a minor amount of fuel (vinegar, vodka). I did use bacteria from a vial to get mine going... it still took a while for it to really get going. I'm sure using some bio balls you already have will speed it up. I would avoid using reborn as it's quite small and will likely lead to clogs. You'll want to use the largest media available. Even with the 1" spheres I found my flow got really bogged down early in the process. You may not see that since your NO3 is already quite low. Mine was out of control.

These reactors can be VERY powerful in terms of reducing NO3! Mine went from over 200 to 2.5 (!!) in about 10 months or less and I wasn't trying to drive it down super quickly. But that is what you can expect in efficacy.

For your situation, I'd just use a small reactor and dose it very lightly with vinegar (vodka is too strong). Make sure to monitor carefully.