Tin issue solved!!

[hllb]

I was fighting with tin for last 6 months. SPS were slowly dying, all home tested water parameter were fine. ICP confirmed high level of tin several times - 0.17mg/l, 170 ppb. I bought new thermometer sensor, new heater, new pump…corals kept dying, new ICP tests proved high level of tin. I decided to change 40% of water volume every two weeks. No improvement. I discussed possible causes with local fish store, people in local forums, read all articles about tin, no help. I had bad dreams, being very tired from this hobby. Then I met a friend who is working in chemical industry and he introduced me to chemist doing a research for large chemical factory using their own icp machine! In my home town! First, we did 5 tests to isolate the major source. We tested RO, new salt water, balling parts, tank water…tin was in fresh salt water and in the tank of course. Then we did another set of tests for all items used in the process of new salt water preparation - white plastic 50l barrel, eheim pump, hose, salt…all soaked in the bucket with about 3 liters of RO water. The test results were very clear - my 6 month nightmare was caused by 130cm of green hose!!! Tin is used as a softener in PVC. It was the hose that came with

aquarium syphon gravel cleaner​

I hope my story can help many of you!

Curious how long the hose was exposed to your water. Did it sit in it for a longer period of time or did it leach out really quickly?

 

[Randy Holmes-Farley]

CONFIRMED! The results from the ICP came back yesterday and exactly confirmed my suspicions... the blue airline tubing on my dosing pumps leaches tin!

1) the new saltwater that sat for months in my mixing container in contact with a rotomold tank, braided flexible tubing (BRS), and orange pvc with schedule 80 fittings (BRS)... Results: zero tin.

2) the 8" long piece of blue airline tubing that soaked in a half cup of RODI water for 48 hours... Results: 5130 ug/l tin!!!

This water also came back with the following contaminants that were not detected in prior analysis of the RODI water....
Silicon 147 ug/l
Copper 3.07
Zinc 18.89

I never thought it would be this high... I was thinking I might see a few ug/l... But 5000+!!! Wow!

All dosing pump tubing has been replaced with RedSea brand tubing. This material appears to me to be made of rubber (though the packaging doesn't say). I have confirmed from others who use this tubing that they have zero tin on their icp tests, so hopefully my Tin problems are solved.

Thanks for the update!

 

[Randy Holmes-Farley]

That value seems extremely high for just soaking for 2 days with no flow thru it, but anything is possible.

It may not come from the inside, but the entire outside of the tubing is constantly exposed.

 

[Reefer Dan]

Any reason to suspect that tin is used with polyethylene (RO tubing)?
Seems from what these posts have investigated is vinyl tubing/pvc.

 

[TexasReefer82]

Any reason to suspect that tin is used with polyethylene (RO tubing)?
Seems from what these posts have investigated is vinyl tubing/pvc.

I have many feet of RO tubing running from my RO unit to my mixing container and the water from the container is consistently zero tin... So I think we can exonerate RO tubing.

 

[Dr. Jim]

It may not come from the inside, but the entire outside of the tubing is constantly exposed.

Right, but the fact that there was no flow (inside or out) and he still got a high value is what surprised me, along with the fact that the tubing surface area is so tiny (compared to my "experiments" using 3/4" tubing with a high flow thru it for several days.)

 

[Randy Holmes-Farley]

Right, but the fact that there was no flow (inside or out) and he still got a high value is what surprised me, along with the fact that the tubing surface area is so tiny (compared to my "experiments" using 3/4" tubing with a high flow thru it for several days.)

I think it would be interesting to see if high flow or low flow or no flow made much difference.

The slow step is likely diffusion through the near surface regions of the plastic (diffusion of organic molecules inside of plastic is very slow), not diffusion away from the tubing once it contacts the water, thus I'm not sure flow will matter too much.

 

[Muffin87]

When I started reefing in 2018, I read you should stick to silicone hoses for safety.
I thought that sounded like excessive precaution, apparently not!

I've bought "food-grade aquarium-use" silicone tubing off AliExpress in the past. I wonder if you can trust silicone tubing not to contain any heavy metals?

 

[Randy Holmes-Farley]

When I started reefing in 2018, I read you should stick to silicone hoses for safety.
I thought that sounded like excessive precaution, apparently not!

I've bought "food-grade aquarium-use" silicone tubing off AliExpress in the past. I wonder if you can trust silicone tubing not to contain any heavy metals?

Just as a note, some tin stabilizers are food use approved.

 

[TexasReefer82]

Just as a note, some tin stabilizers are food use approved.

Randy, What's your take on the traces of Copper and Zinc? Are these metals used in plasticizers as well? I assume that the elevated Silicon came from the tubing - perhaps it's silicone tubing.

 

[Randy Holmes-Farley]

Randy, What's your take on the traces of Copper and Zinc? Are these metals used in plasticizers as well? I assume that the elevated Silicon came from the tubing - perhaps it's silicone tubing.

zinc oxide is sometimes used as an acid scavenger in plastic. Don't know uses of copper in plastic.

Si could be some dissolving polymer or something else, and I would not worry about it.

 

[Careefornia]

Based on my experience, the levels are getting lower over time but very slowly. In my case, it was leaching for more than 6 months and the last test - just submerging (no pressure) of the hose into 3 litres of RO water for 24 hours resulted in 490 ppb/l of tin!

Chinese made products

 

[Randy Holmes-Farley]

Chinese made products

Why do you believe that?

Tin is a high value additive for plastics made and sold by many companies, including some headquartered in the USA. It can be pharma grade for pharmaceutical uses.

 

[john90009]

@Randy Holmes-Farley have you ever come across anyone raising this question with the waterbox tubing? It is quiet malleable and I’m afraid if I were to remove it and try to fit on a different tubing I don’t want to jostle the return pvc tubing up in the tank. Does the tube endlessly leech? I am getting tin around almost 20.

 

[Randy Holmes-Farley]

@Randy Holmes-Farley have you ever come across anyone raising this question with the waterbox tubing? It is quiet malleable and I’m afraid if I were to remove it and try to fit on a different tubing I don’t want to jostle the return pvc tubing up in the tank. Does the tube endlessly leech? I am getting tin around almost 20.

I’ve not kept track of tubing types suspected of releasing tin, but I do not recall hearing that one mentioned. Tin release will start faster and slowly decline over time, but I do not know the time fram for it to go from a concern to not a concern. Weeks? Months?