Help me understand (excess) Iron in the reef tank

PedroYoung · Jun 30, 2020

So I have been getting increasing levels of Fe in my Triton ICP tests over the last yr. Going from
zero March 2019 (and for years previous), to
0.6 mg/l in August, to
4.34 mg/l in Jan, to
3.2 mg/l in May.
Been trying to figure out where it could be coming from. Very little going on in my tank (return pump and skimmer plus heater, and MP10's). Have checked everything multiple times for leaking/swellling. I am on a well with an iron removal system. Also use a RODI system with RO, then BRS ProDI (separate Anion, Cation, mixed bed) then through another mixed bed. I use Tropic Marin Pro Reef salt and ESV 2-part. I do about 10% weekly water changes. I finally sent off a salt water sample of 24hr mixed fresh saltwater. Came back 11 mg/l!!!. So my water treatment guy is coming back to check out the iron removal system, but I've seen no evidence of those high levels of iron in the house (laundry, drains etc). I took apart the Mag5 pump I have been using to mix the saltwater and there was def a problem, the ceramic impeller shaft was broken. I can't see any signs of swelling/leakage in the magnetic part of the shaft but possible that's where something is happening.

Any feedback on what should happen with Fe in RODI system?

Is there an Iron test for this type of situation? Will freshwater iron tests work in salt water? I see Red Sea had a Iron-pro kit, but doesn't look like anyone carries it anymore.

I'm planning on having my water guy test with his test designed for freshwater
1-water at the tap where I pull my RODI from
2-my RO bin
3-saltwater I mixed with the Mag5
4-saltwater I mixed in a container using only a SS wisk

I've been seeing issues with zoas since last yr when Fe first started creeping up, also seeing some mortality in LPS (chalice and favias). SPS seem ok so far, maybe color off somewhat. All my other parameters are spot on with where I'd like them. Only aberration in the last (fresh saltwater) test was high level of Manganese (102 mg/l) which I've never seen in any of the tank tests (always comes back zero).

Any feedback from knowledgeable chemistry types would be appreciated.

sfin52 · Jul 1, 2020

What's the tds of your water? Chance of channeling in the di? What ate you using top clean the mp pumps?

Randy Holmes-Farley · Jul 1, 2020

4 ppm iron? That seems implausible.

You sure it isn't ppb? (ug/L)

PedroYoung · Jul 1, 2020

sfin52 said:
What's the tds of your water? Chance of channeling in the di? What ate you using top clean the mp pumps?

coming out of the RO it's 2, leaving the mixed bed it's 0.

sfin52 · Jul 1, 2020

PedroYoung said:
coming out of the RO it's 2, leaving the mixed bed it's 0.

What are you cleaning the pumps with

PedroYoung · Jul 1, 2020

Randy Holmes-Farley said:
4 ppm iron? That seems implausible.

You sure it isn't ppb? (ug/L)

You are correct! That makes a big difference in interpretation (just a little squiggle makes all the difference). Can you address the DI question for the Fe and maybe the effects of Fe at these "elevated" levels (not as elevated as originally thought, but still concerning to me)?

PedroYoung · Jul 1, 2020

sfin52 said:
What are you cleaning the pumps with

I haven't been cleaning the mag 5 powerhead with anything. I've been using it just as a utility pump to circulate freshly mixed saltwater (24 hrs), then to transfer from brute to tank during water changes. I've never cleaned it, but it's never really been "dirty", just sometimes a little brown/red build up. The impeller is broken now though. Took it apart for inspection while tearing out my hair and it was cracked (ceramic shaft).

sfin52 · Jul 1, 2020

I would be surprised if the iron is 4ppm with 0tds

Randy Holmes-Farley · Jul 1, 2020

PedroYoung said:
You are correct! That makes a big difference in interpretation (just a little squiggle makes all the difference). Can you address the DI question for the Fe and maybe the effects of Fe at these "elevated" levels (not as elevated as originally thought, but still concerning to me)?

If the iron is 4 ppb, that's not a concern. I dosed to just a little under that.

RO/DI removes it quite well.

From my ICP article:

My Triton Testing Results: By Randy Holmes-Farley - REEFEDITION

Recently, Triton GmbH in Germany has initiated a method of testing many ions at once for a single price. In the US, that service is coordinated by Unique Corals. For $49 they will send you a couple of tubes to collect a tank water sample, and a prepaid mailer to send the sample back to them...

www.reefedition.com

Iron (Fe). The natural iron level varies a lot with depth, but surface seawater may have only 0.006 µg/L. The Triton LOD = 0.3 µg/L. I dose iron, and when I dose it I boost iron to roughly 1-2 µg/L, which would be detectable. This sample was taken more than a week after the last iron dosing, and none was detected as it gets depleted in the meanwhile. I’ve not yet seen a Triton test result for a real aquarium sample that had detectable iron, but that doesn’t mean these tanks are necessarily deficient. Iron is also a case where the form is critical, and ICP cannot distinguish form. Binding to organic matter, for example, can alter the bioavailability of iron.