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

olonmv

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Hi guys, up to page 45 of this thread, thinking of building one of these units 4” by 3’ tall, tank 2000L and nitrates below 40 , quick question is some of these have a small tube from left to right tower, is there a reason for smaller tube or can it just be a U tube type between the two chambers , thank you , based in the UK
I tried to build mine off of scale to Donovan’s. If my math is correct, using a 4” pvc pipe, yours would need to be over 200” long.
 
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olonmv

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If you’re trying to filter a 2000L tank your DND would have to be sized to hold about 47L (when void of media). The dnd flow rate needs to be flowed to cycle the DND volume by 2-4 times a day (5-10%) of tank volume in a 24 hr period. At least that’s how I’m seeing it. I have a nano tank and just started up a mini DND that I think I scaled it down correctly. I’m on day 3. Today is when I’m supposed to introduce a carbon source.

If I’m correct…..a 10” PVC at 36” long is what you’d need.
 

Reeftank2008

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Hi guys, just in middle of a build too. My tanks 500 litre and I have made a tower out of 3" pvcu pipe. I have 4 litre of seachem matrix to add and 5l of fluval ceramics too.
I've got a rubber end where carbon will be dosed and the other is a solvent weld cap so no air can get in....

Should this be OK for my size tank?

Finally if I tap in the side of the outlet on the tower won't I have a air pocket at the top?


Sorry forgot to add the length of both towers is 23"...
16623932642934562225944983972867.jpg
 
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olonmv

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So is they a need for smaller pipe between them ?
10” wide wow.
I’ve got 5 litres of matrix and 6 boxes of 1.5 spheres marine pure, no way enough lol
The length and size I mentioned for you is a straight run no bends. That’s how I did mine. Flow and travel time seem to be the key in this build.
 

olonmv

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Hi guys, just in middle of a build too. My tanks 500 litre and I have made a tower out of 3" pvcu pipe. I have 4 litre of seachem matrix to add and 5l of fluval ceramics too.
I've got a rubber end where carbon will be dosed and the other is a solvent weld cap so no air can get in....

Should this be OK for my size tank?

Finally if I tap in the side of the outlet on the tower won't I have a air pocket at the top?


Sorry forgot to add the length of both towers is 23"...
16623932642934562225944983972867.jpg
I’m compelled to say 4” pvc at 23” each tower would be correct scale.
 

Steve2020

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A U tube is fine. There is an example in this thread where someone used a U tube and glued small PVC pipe to the U pipe so it would stand up. In my case I used two 4"x1'x4" tee's with a 1" tube connecting the two tee's with plugs glued on the bottom of the tee's so the DND would stand up.
 

Gudhjem

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Anybody else that has a tall U-shaped DND ever have an issue with a vacuum/siphon on the discharge when you stop the feed and if so what did you do to fix it? I'm pretty sure I am not the only one that has a tall external DND, and I have not read about any siphon issues.
Looks like you got it sorted, but yes, siphoning does seem to be an issue with the DND. My discharge hose originally extended downward toward my tank, until I realized the siphon meant my towers were less than half filled (even with flow on). The discharge opening, or end of hose attached to it if you use one, will be the height of the water in the towers if they are sealed. you can also vent the discharge opening as you did to avoid the siphon. I see a lot of setups in this thread that don't seem to do this, and I wonder if the towers are siphoning to a low fill level.
 
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Steve2020

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I’m compelled to say 4” pvc at 23” each tower would be correct scale.
You think a 4" pvc at 23" each tower is big enough for his 525gal tank? That seems awfully small to me. My 54" 4" inch pvc each tower with media installed only holds 4gal of water. The size you mentioned will hold less than 2gal. With his size tank and using the 10% rule he needs to run 52gal per day which is 2.16gal per hour which puts his stay time water contact in the DND at less than 1hr. Seems pretty short to me IMO.
 

olonmv

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You think a 4" pvc at 23" each tower is big enough for his 525gal tank? That seems awfully small to me. My 54" 4" inch pvc each tower with media installed only holds 4gal of water. The size you mentioned will hold less than 2gal. With his size tank and using the 10% rule he needs to run 52gal per day which is 2.16gal per hour which puts his stay time water contact in the DND at less than 1hr. Seems pretty short to me IMO.
This is for 500L (132 gallons). The 525 gallon (2000L) I feel it should be 10” at 36” long.
 

Steve2020

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Looks like you got it sorted, but yes, siphoning does seem to be an issue with the DND. My discharge hose originally extended downward toward my tank, until I realized the siphon meant my towers were less than half filled (even with flow on). The discharge opening, or end of hose attached to it if you use one, will be the height of the water in the towers if they are sealed. you can also vent the discharge opening as you did to avoid the siphon. I see a lot of setups in this thread that don't seem to do this, and I wonder if the towers are siphoning to a low fill level.
I tend to agree with you that some DND's on this thread may not be filling properly. Also I am not sure how some of the DND's you see on here have a so called solid flow unless they have an extremely large tank/sump water volume. My total water volume is 255gal and at 10% max turnover that would be 1.0625gal/hr. I am flowing a measured 1.071gal/hr ( 1gal in 56min ) and you can see in the video it is not a solid stream. I am running 3/8"OD tubing. I also tried 1/4"OD tubing and it was still pulsating.
I just finished the DND build and it is up and running. I also put a vent tube on the emergency line just to be safe. The syringe on top of the tubes is for manual dosing of MB7. I just measured NO3 and it is at 19.6ppm by Hanna and 20ppm by API so we will see what happens in a few weeks.
 

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Steve2020

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If you’re trying to filter a 2000L tank your DND would have to be sized to hold about 47L (when void of media). The dnd flow rate needs to be flowed to cycle the DND volume by 2-4 times a day (5-10%) of tank volume in a 24 hr period. At least that’s how I’m seeing it. I have a nano tank and just started up a mini DND that I think I scaled it down correctly. I’m on day 3. Today is when I’m supposed to introduce a carbon source.

If I’m correct…..a 10” PVC at 36” long is what you’d need.
olonmv, you wouldn't happen to know how much bacteria to add daily for the first 3 days in respect to DND volume? I added 25ml today which is what I was dosing in my tank when I had a dino issue.
 

olonmv

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olonmv, you wouldn't happen to know how much bacteria to add daily for the first 3 days in respect to DND volume? I added 25ml today which is what I was dosing in my tank when I had a dino issue.
What I did was take Donovan’s volume and divide it by mine to get my multiplier. In my case it was 5.92. I took the multiplier and divided by Donovan’s 5ml and came out with just under 1ml. In your case you’d multiply by the multiplier. I get a multiplier of 3.15. So 3.15 x 5= About 47ml. I take it since it’s a slow flow all that is supposed to be consumed in the DND instead of in the DT.
 
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Steve2020

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@Steve2020 bacteria for 5 days, carbon introduced along with bacteria on day 3. Unless I’m reading it wrong.
Yea I just noticed that. Thanks for catching that. What was Donovan's tank water volume? I saw he mentioned his 10gal sump held 5gal. Also I need to figure out how much DIY carbon to add on day 3. My DYI carbon is very similar to NoPox.
 

olonmv

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Yea I just noticed that. Thanks for catching that. What was Donovan's tank water volume? I saw he mentioned his 10gal sump held 5gal. Also I need to figure out how much DIY carbon to add on day 3. My DYI carbon is very similar to NoPox.

Your welcome. I believe I read it to be a total of 80gallons including his sump. I just added straight vodka. Maybe I’ll try my hand at Randy’s recipe but if the vodka works I’ll be stoked and just stick with that.

Edit: Sorry,I just caught that. Carbon will be same dosage amount as bacteria. Mr Donovan was doing 5ml a day of bac for 5 days and 5ml of carbon from day 3 on.
 
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olonmv

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What I did was take Donovan’s volume and divide it by mine to get my multiplier. In my case it was 5.92. I took the multiplier and divided by Donovan’s 5ml and came out with just under 1ml. In your case you’d multiply by the multiplier. I get a multiplier of 3.15. So 3.15 x 5= About 47ml. I take it since it’s a slow flow all that is supposed to be consumed in the DND instead of in the DT.
NOT 47ml!!!!!!…….15.75ml. Not sure where my calculator was getting 47.
 
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Reeftank2008

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It's now filled with media... I used FM zeolite in the bottom of each tower upto the branch. I then filled up the remaining with fluval bio-fx and seachem matrix. Tomorrow the bulkheads should arrive so I can fix the tops on and should be good to go.....

IMG-20220906-WA0002.jpeg
 
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