Sulfur Denitrator Help

Ed Kaz · May 3, 2026

Hi, I have been trying to re-start my Korallin Biodenitrator S1502 and can't seem to get it going? It ran GREAT for a year ... 4 months ago I tore it down to clean due to the crap that was in it. Cleaned with DI water and replaced media (DELTA High Purity Sulfur Reactor Meda). When I started the reactor I ran the output wide open for a few days then lowered output drip rate to a drip a second for the last 4 months. The nitrates levels still have not changed in 12 weeks ? Nitrates @ 80ppm from reactor output. Is there something I can dose to seed reactor (would MicroBacter 7 or something else work?). I have some BioDigest and Bioptim that I have not used (was going a different route with a Reef Octopus bio-churn reactor) I could not find a "freshness date" on box? Just was wondering why or what bacteria is needed. The only thing I dose is All for Reef. Tank is 300gal. and been set-up for over 17 years mostly fish only (porcupine puffer makes a mess!) with a few rose anemones and hammerhead corals.

Thanks for any Help
Ed

Randy Holmes-Farley · May 3, 2026

I do not know if any commercial bacteria additives have species that will colonize the sulfur, but I would doubt it.

Have you tried upping the flow or measuring nitrate in the effluent?

Ed Kaz · May 4, 2026

Hi Randy, thanks for getting back to me. By effluent, do you mean the reactor output? Yes, this is where I measured it with a hanna digital tester. I sure can increase the output flow, but I thought very slow drips are what is needed so bacteria can colonize, then increase flow? Attached is the instructions from korallin...
Thank Again

Randy Holmes-Farley · May 4, 2026

So you measured the reactor output and got a value of 80 ppm (I see that now). Did you compare that to the tank value?

Ed Kaz · May 4, 2026

Yes they are both the same.

Ed Kaz · May 4, 2026

I will give it a few more weeks and then pitch it....
BTW:
Do you have any opinion on the Reef Octopus bio-churn reactor? Is it worth the trouble?

X-37B · May 4, 2026

It took around 2 months for my no3 reactor to get effluent to zero. I used a Kamoer and pulled from the sump. It takes time so no hurry.
I actually took mine offline and dose vodka now. Simple, easy , and effective.

Ed Kaz · May 4, 2026

X-37B said:
It took around 2 months for my no3 reactor to get effluent to zero. I used a Kamoer and pulled from the sump. It takes time so no hurry.
I actually took mine offline and dose vodka now. Simple, easy , and effective.

I have been in it for 4 months! No change? It hurts nothing to run it. Like I said I will give it a few weeks. Thanks

X-37B · May 4, 2026

Slow the drip rate down until the effluent is zero and adjust from there. If effluent is the same no3 as the tank it needs more dwell time to lower it.
If its been 4 months it is going to fast through the reactor.

It may not hurt anything but it will lower the ph of your system.

adamsfour · Jul 3, 2026

Just a guess I suspect it could be the sulfur you used. I am using a Deltec reactor with their sulfur and it took 4 weeks to reach zero.

Dr. Reef · Jul 3, 2026

I have used sulphur denitrators for decades. Advise given above is correct. You need to slow it down till No3 hits low to 0 then open it up slowly and keep on increasing slowly making small adjustments daily openning its flow up till desired levels are reached.

Bacteria you are looking for need 0 oxygen environment, That will not be achieved with moderate flow running through. This is why you have to slow it down and cause the bacteria to grow and once they grow, do not open the flow fast. always make very very small adjustments keeping bacteria alive away from O2.

backbayreef · Jul 3, 2026

Many sulfur denitrators (including your Korallin) has a port for a pH/ORP probe. I’m using an ORP probe and control drip rate with the Kamoer. You’ll want to land ORP around -200 to -250mV. The effluent should be around zero once you’re in this zone.

You can see me tinkering with it here:
https://www.reef2reef.com/threads/backbayreef’s-450gal.1066683/post-14243685

aussiejohnny · Jul 4, 2026

i had a sera bio denitrator 40 yrs ago (yeah im older ) used to have tablets that went in the top of the dripper ..water dripped over them into the main reactor ..i am probably wrong but i think it was like a carbon source ...i remember the starting drip rate was 15 drops per minute took 2 months to do anything and when it did get going had to speed up the drops an test nitrate either end each day ..worked great but so fiddly ..rather use nopox..same result

backbayreef · Jul 4, 2026

NoPox (or carbon dosing methods) did not work for me since the process generated too much nasty slime in the sump, clogging up reactors! On big tanks, you’ll need to increase the carbon source up to 60-70mL to be effective.

I do 10mL of vodka on my 90gal & 150gal tanks and it’s stupidly easy and low maintenance.

JumboShrimp · Jul 4, 2026

I gave up on mine.

In fact I have a second unopened one still in the box. (I did a long R2R thread on my experiences.) Sounds like you are getting good advice here.. hang in there, I blame myself. Lol.