I think you will notice the rotten smell long before it may become dangerous, unless of corse you are away from home,
I also wonder how bad is the clogging issue (drip rate reduction) that some people reporting (in the above provided links)
At any rate this is exitining to be able to feed corals and fish better diet and still have low No3.
Does anyone knows where to buy media in Vancouver?

I would argue that this is the only way to go for nitrate reduction on large systems. I initially went with two Phosban reactors to test the concept for myself, before committing to a larger unit :razz:

Seeing the test reading of zero nitrates out of the reactor was like magic after struggling with nitrates for a year (we overfeed and that's not going to change ... so we know the source). Doing religious weekly 50 gallon water changes for 2 months steady still only took nitrates from 40 ppm down to 30 ppm, and skipping one week would put us back to the start.

With a DIY reactor based on the Phosban design (two 6" x 36" cylinders), we took the nitrates to zero in 4 weeks on our 500 gallon FO system.

The rotten egg smell can create the occassional "Annacis Island" :redface: as my wife calls it, but can be masked with some burning oils until the flow rate is corrected (too low of a flow rate creates H2S). For those who've driven over the Alex Fraser bridge on a muggy summer day, you will understand the reference to Annacis Island :lol: :lol:

Holey mondo reactor size though! Is there any good reading as to how to size a reactor effectively against a total system volume? Or is it mostly guesswork?

Also is there any mechanism to determine an optimal flowrate through the reactor? How long does it take for the smell to go away after adjusting, if indeed you start off too slow? What kind of flowrate do you have on your reactor?

From what I know, flow rates depend on bioload. It is slightly different for everyone. The .pdf file for the Midwest unit explains how to set your drip rates. (they also cover how to find the optimal flow)

Thanks for the input Lyle, now I really want one. lol

Delbeek and Sprung Volume 3 suggests that the volume of sulphur beads be 1% of the water volume. This book was absolutely the best source for information as I was researching and setting up my reactor.

I have 4 gallons of beads for a 500 gallon system, so a little under 1%. To start off, the flow rate needs to be extremely slow (this is very tricky unless you have a nice system like reeferaddict with fine controls - if Korallin had a much larger unit I would have seriously considered that). The drip rate for starting is in the range of 1 drop per second per half gallon of sulphur :biggrin: - that's tough to regulate in a DIY design!

Once cycled (mine took about a week), flow can be increased to around 1 gallon per hour per gallon of sulphur. The flow range seems to be quite forgiving, unless you can't get the flow fast enough due to constricted tubing ... hence my Annacis Island situation. As the nitrates dropped, I found I needed to increase the flow rate into the 8-10 gallon per hour range. I upgraded to a Mag 7, and still needed to redesign the plumbing with 3/4 inch PVC to get the necessary flow.

The smell can last 2-4 hours before the increased flow gets the H2S under control. It can seem like a long time when you have the rest of the family staring you down :redface: :redface: :redface:

as long as you can smell the h2s your ok :)

Lyle, are you recirculating through the media, and feeding with a separate pump, or are the flowrates you're describing (8-10 gph) refer to the only flow through the media? I sort of get the sense you're not recirculating .. I was thinking I'd still recirculate, much like how a calcium reactor works .. or is that not the recommended approach?

From what I understand you must recirculate. All the reactors are built this way, and then they have a slip stream through them from the Aquarium and back. (some people use a siphon, some people use a pump)

Thanks, that's what I thought too. If you read the "DIY" instructions that Caribsea puts out though, they just have it as a single-pass basis and it sort of sounded like that's how Pansy-Paws does it too (I could be reading it wrong?). I guess that way works too, but to me anything that requires contact time is always better to have it on a recirculating basis.

Well sounds like I'm set then .. I just need some media. I'm gonna have this online within a couple of days (just as soon as I can get my hands on some media!). :cool:

I believe it is this recirculating that helps remove the oxygen from the water to create the anerobic zone. (more effective)

Yes I agree that makes more sense. Like I said though the DIY instructions Carib-Sea talks about looks like single-pass to me, .. you can easily replicate the anoxic zone with a slow enough flow without the recirculation, but I agree it seems easier to do so with recirculation. If the channel was long enough I guess you could get away with it. But anything I would want to build I would want to make it as recirculation because anything that increases contact time cannot help but help.. whether it's a skimmer, reactor, heck even my Phosban reactor I'd like to modify and make recirc.. it just makes sense to me. :)

Given the height of my design (36"), I only have a single water flow thru path, no recirculation.

As indicated, with a slow enough water flow, the anerobic zone can be established.

So I got to the point where I was on the phone to my LFS, asking them to bring in some LSM, and again, the topic came up.. "You realize there's a risk of H2S right?" Aaannnnnd..... arrrrrggggh, there we go, once again, I thought I had made a decision and was going to follow through on it, and here I am, second guessing myself all over again.

Here's my thought ... when I was a summer student I had it absolutely drilled into me how bad H2S is. You can smell it at 1ppm, at 10ppm you can only be exposed safely for 10 minutes at a time (I forget how long you have to wait in between) and I think it's instant-loss-of-consciousness at 100 ppm (it may not be 100ppm, I don't remember. At some point though, you can be dropped instantly with one breath).

Soooooo ... seriously, what are people's thoughts on this? I've even posted this question in Randy Holmes-Farley's forum on RC (although he's not online this week). Keep the tank area well-ventilated?

I may be overly paranoid but one thing I remember is that H2S is heavier than air, meaning anyone closer to the ground is at higher risk (think: pets and small children). Although I need to reduce my nitrates I can't do it if I'm risking the wellbeing of family and pets (or the tank itself).

Maybe Zeovit's the way to go after all ... I don't know ... argh, there I go, second-guessing myself again. :(

I don't have any experience with the biodenitrator but can I do know a little bit about H2S from the job. 10 ppm is the maximum concentration you can be exposed to during an 8 hour work day, so H2S is not a great risk at that level, but with the smell at that level your wife and family may be! 100 ppm will cause watery eyes, respiratory problems and nausea, and 200 ppm gets you close to the death range within hours. Above 500 ppm your life span is minutes and at 700ppm death is almost immediate. It is nasty stuff and kills a few people in the oil industry every year.

As you mention, H2S is detectable at very low levels but is very toxic and will collect in low spots so for me personally it's a piece of equipment that I would only use if the worst case H2S production rate is low, the area is well ventilated to the outside and you can check up on the equipment frequently.

Ok those numbers are a lot higher than what I thought they were. I was an oilfield worker as a summer student but those days are long behind me so my memory was clouded. I would think 700ppm would be hard to do, even playing with elemental sulfur, i.e., one would notice the smell @1ppm long, long, long before.

I agree, and with these things I'm sure you're dealing with pretty low volumes produced. The danger is the accumulation if the tank equipment is in an out of the way place in the basement like mine is.

Having used a denitrator with 4 gallons of LSM, I'm not really concerned on the toxic front. For one thing, if this was an issue for this application we would be seeing warning labels up the ying yang, and would have confirmed lawsuits from the US. If that was the case, I doubt that Caribsea and Korallin would still be marketing their products ... too much liability given our litigious nature (ever notice how many warning labels are on ladders these days :smile:).

I'll definately concede that for industrial settings, this can be serious stuff. However, Delbeek and Sprung devote 7 pages to sulphur denitrification, and only a couple sentence mentions of hydrogen sulfide smell as an issue, mainly around the ambience impact of a smelly living room. The chemical reaction from Holmes-Farley shows:

2 H2O + 5 S + 6 NO3- ---> 3 N2 (gas) + 5 SO42- (sulphate) + 4 H+ (hence slightly acidic effluent and the reason for calcareous material after the sulphur)

so no H2S is emitted in the primary reaction, unless the flow is too slow and secondary chemical reactions occur. As you mention Tony, the 1 ppm level will provide ample nasal warning before the level can rise to dangerous levels (which I doubt is even possible ... as this application has been used in Europe for over 10 years on some massive aquariums).

Also, with a recircuation system, the volume of sulphur would be much less than even I'm using.

H2S can be smelt in concentrations as low as ppb (parts per billion). It definately is a gas that is not something to laugh about. I happen to work in an oil/gas plant where we have vessels containing 800,000 ppm. (yeah, more than enough to kill a small town off)

That being said, I do not think these reactors have the ability to make it in such high concentrations. Perhaps maybe if it were to go for weeks on end without being noticed. (pump failure) And then you opened it up to atmosphere, but even then I doubt it. Just keep your nose out of it and clean it in the bathroom with a fan on and you'll be fine. Kalk or Carbon dust is probably more harmful to your lungs than the small dose of H2S these would give off. If you are diligent and check your equipment regularly, I don't think there would be a problem.

There was one person on a forum who's reactor stoped recirculating and was sending H2S into the tank. His fish developed lesions and his corals didn't look so good. Once disconnecting the reactor things cleared up right away. (I believe he may have lost one fish) So in a sense you should be able to spot the problem before it becomes serious. Just think, his fish didn't just suddenly die, and the LD50 would be super small for fish compared to a human. (body mass)

I am on the verge of ordering a unit from Midwest Aquatic...

Cool. I looked at those and if I wanted to buy a unit I'd probably consider one of those. However I seem to have a collection of unused calcium reactors (I seem to have at least 2 that I'm just sitting on) on top of the one I have in use ATM, so I think I'll just convert one of those for now. I don't see any reason why it wouldn't work. Might need to go to a bigger reactor when I get the 280g going but that's down the road anyhow, and I wouldn't mind DIY'ing something at that point anyhow.

Anyhow good luck with yours. :cool:

Yeah, I think that is a good bet. If I had a few calcium reactors lying around I'd probably do the same.

I'll post my findings/results in this thread. (if I buy one)

My LFS started running a couple of them, and I think it IS a Ca reactor. He's been playing with one, and now runs it with bottom half sulpher, thin foam divider, top half Ca reactor media. There's an ORP probe in the top, and the ORP is controled by the output flow. It's putting Ca into the system, and dropping the Nitrates also. He's super horned up for these things, think's they're the cat's a$$. He says that once the Nitrates are down to 0, the output will be almost fully open, then gets opened all the way so the bacteria don't die, they may diminish, but continue to pull Nitrates as they're produced. AND the unit has an impact on Phosphates also, not huge, but noticeable.

Pansy-Paws, Where do you get your sulphur media from? Wine shops like posted above? or somewhere else?

I thought this excerpt should be posted here:

When dissolved in water, the smell depends strongly on pH (which determines how much is in the volatile, hence "smellable," H2S form). Humans often can just detect hydrogen sulfide odors when the concentration is above about 0.029 ppb in freshwater. In seawater at pH 8.2, where only 6% of the sulfide present is in H2S, this odor threshold is likely higher, perhaps on the order of 20-fold higher (0.6 ppb). Fortunately, that threshold is below the lethal limit of many aquatic organisms (usually above 5 ppb; sometimes as high as 50,000 ppb), so odor often can be detected by humans before hydrogen sulfide rises to acute, lethal concentrations in reef aquaria.

Taken from here:

H2S & Reef Aquarium:
Randy Holmes Farley

http://www.reefkeeping.com/issues/2005-12/rhf/index.php

I got my sulphur media from J&L ... in the form of Caribsea LSM. Never thought of wine stores at the time, probably much cheaper if you can find it.