I've decided to try a sulfur denitrator. I feed my fish generously, so although I do the water changes, do heavy skimming; I tend to run with nitrates.
I had at least two functioning calcium reactors, only one of which I'm running, so I picked up some Caribsea LSM (elemental sulfur beads) and filled the smaller of the two I had (leaving the midsize unit to still run as a calcium reactor).
I guess technically this isn't so much an experiment to see whether a sulfur denitrator will "work" per se (there are enough testimonials to show the theory is sound), in my case it's more an experiment to see if I could use my smaller reactor as an effective remover of nitrate. It's a very small reactor and only holds approx 1/3 of a container of ARM (or sulfur, in this case).
I used the second stage of my midsize calcium reactor, filled with ARM, to buffer the low pH output of the sulfur reactor.
Unit is recirculated with a Mag2 pump, fed by a minijet powerhead in the sump. The output of the first stage is a John Guest style ball valve for 1/4" tubing and that is closed most of the way, in order to produce an effluent drip rate of 1 drop per second.
I put the unit online on Monday evening.
First challenge was trying to find the valve position to create a steady driprate. I find after 24 hours it tends to have slowed, so I might need to adjust the feed pump situation (I'm currently looking for an Aqualifter pump to see if I can produce a more consistent drip rate with that.).
I'm running the unit on my ritteri tank, which, after a recent skimmer problem that I only fixed about a week ago, has rampant nitrates at 75ppm (the anemone can handle it, it's lived in as high as 80ppm in the past .. there are no corals in this tank .. if there were, they wouldn't be for long at that kind of level!!
).
pH in the tank runs about 8.2.
After 24 hours, pH of the effluent had not dropped significantly (8.1).
After 48 hours, pH of the effluent had dropped to 7.8. Tank still at 8.2, so a 0.4 pH reduction already.
After 72 hours, pH of the effluent has dropped to 7.5. Tank still at 8.2.
There is no sulfurous scent to the effluent whatsoever at this point.
My next plans are to, at the one week point, test the nitrate level of the effluent and compare to tank water, to see if there is indeed a reduction.
I also want to test pH before the second stage and compare to the pH after the second stage, to determine how effective the volume of ARM I'm using is at buffering the output of the first stage.
My main concern is to see whether the small volume of media is enough to create the anoxic zone required for the anaerobic bacteria to take hold. Even with a flowrate as slow as 1 drop per second (roughly 10ml/min), I'm concerned this could introduce too much oxygen into the first chamber. Time will tell.
To convert the calcium reactor into a sulfur reactor ... the main difference is you don't inject CO2 into the sulfur reactor. So you need to close off or remove the CO2 injection port. In my reactor it's a T fitting on the pump intake. I decided to leave the "T" in place because I may go back to using it as a calcium reactor and this way I won't lose the T fitting. Instead I just inserted a small piece of tubing with an irrigation dripline plug to cap it off.
Here are some pics:
First stage filled with LSM beads, recirculating; feeding into single-pass second stage filled with ARM.
(The braided hose and green tubing are not related to this reactor. Same for the red tubing, which is my FW topup line...)
A closeup of the feed line into the T, which is capped off on the unused direction (which is ordinarily used for the CO2 feed):
