So the official word from GE is that all GEII silicones now contain petroleum distillates as a mildew inhibitor. Unofficially, this hasn't always been the case. My friend used to be a chemist for GE and he has told me several times now that only the Kitchen and bath version had this. He's surprised that we're even having this problem and didn't know abou the switch. So it seems they've changed it in the last year and a half or so, and this is why so many people have used it in the past without issue.
On all of the GEII bottles I have it says 100% silicone and makes no mention of the 1 to 5% mildew inhibitors. I guess it's too hard to write "95% of this product is 100% silicone". Previously only the GEI and GEII kitchen and bath had the inhibitors; seems like the "premium" line of GEII only now carries his option.
When I chose GEII for my tank I did so for strength and quality rather than price, and on the recommendations from several reefers and a guy who used to work with the stuff. The chemistry behind GEII allows for a better bond to glass and has less tendency for the inside seems to peel away from the glass with age, so you don't get the tattered look some old tanks get. It also has more give to it while being stronger and has better resistance to the elements (ie. Salt water). This formula though evolves ammonia rather than acetate; however, it is "supposed" to cure much faster. It is spposed to be minimum 3 hours to water ready, 8 hours to moderate strength and 24 hours to fully cure. Bare in mind this is not accounting for the evolved ammonia to dissipate. I've seen several threads where people make emergency repairs with GEII and fill the back up with water in 8 hours without I'll effect. Most tanks "should" be able to handle the relatively small cycle caused bathe ammonia is there was some still there. When I built my tank I let it cure for almost a week and a half, filled it with water for 48 hours twice and gave it angood clean... And I still had a problem when I transferred, so I doubt it was the ammonia and likely an effect of the inhibitors. Big tanks probably notice this less due to dilution. Had it been more readily available to me I would have gone with a RTV silicone that was aquariums safe, but since it wasn't GEII was the strongest, supposedly "safe" product available to me.
When I swapped my tank there were 7 other more probable causes for my problems (temperature swing due to a faulty heater, reusing old sand, broken skimmer shaft so only a small back-up skimmer, etc), so I never suspected the silicone. Seeing what is happening in this tank and having got this other bit of info this morning from GE, I am more suspicious of GEII being the cause but bottom line is: it's officially not reef-safe.
The inhibitors may have caused die off of microfauna which may explain the ammonia spike, rather than ammonia from the silicone itself. If anyone is reading this and having problems with GEII, run lots carbon to remove the inhibitors that may be leeching into the water column. The direct effects of whatever was happening seemed to dissipate within a couple weeks in my tank and was just a long road to recovery. They tank is healthy and happy now and the corals are growing like weeds like nothing ever happened, so it doesnt look like there are major long term effects from the silicone (if that was the cause), just an initial hit.
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12-29-2011, 08:49 PM
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