[TybaltTinc]

alright guys, I used two types of silicone, ge silicone I clear for waterproofing and sealing the water area, than i went back over it withge silicone II black to press my substrate too. i let it sit about a week or two and put water, plants etc in it. its waterproofed and leak proof beautifully, but ive tried twice now to put fish in it, and both times they have died over night. is it possible the silicone or great stuff foam could be leaking some kind of toxins into the water?

 

[VivariumWorks]

Possible but very unlikely. The silicone won't be releasing anything toxic, even if its uncured, but if it was you'd know because it would still be sticky.

The polyurethane foam doesn't release anything toxic into the water until LONG after it has been exposed to UV and weathering and even then its only urea which plants/nitrogen cycling will absorb. If your foam was uncured you'd know, it wouldn't be hard and I've yet to come across an uncuring batch of "great stuff" after well over 2 pallets worth of usage.

Your problem most likely lies in the water's dissolved oxygen level. The water is likely not aerated enough to support the fish at this time and it is likely asphyxiating them. That or your pH is way off due to water/soil contact. I would test the water using a standard litmus test strip they have for freshwater systems and if it all comes up good, then its probably your DO. Do the fish look like they are "gasping" at the surface before they die, because that is typical indicator that your DO is too low. Bubbler or dramatic increase in surface area to volume ratio will be needed. (Waterfalls can do this but only when done right.)

 

[froggymike]

Read the directions on the silicones. All of them say on them not for aquarium use. I have always used specific aquarium silicone and have never had a problem.

 

[Ed]

If the silicone II is not cured all of the way, it is also pumping ammonia into solution which could result in elevated nitrite and nitrate levels. Also there is the possible issues with the organotins in the silicone II. See
http://www.dendroboard.com/forum/parts-construction/35720-bio-seal.html


Ed

 

[VivariumWorks]

Was your silicone still sticky even after you applied it? If not then its not likely that.

And the whole "organo-tin" thing, just doesn't have enough evidence to be supported of killing darts/fish. Considering thats been used in breeders dart tanks for as long as it has, if it was as big of an issue as its pushed in that thread, then we would have known about it long ago. Not a believer. I'd just rather not breath in large volumes of acetic acid by using the lower grade silicone when the higher grade functionally works the same.

Check your water with a typical dip strip, see what that comes up, and from there you can make your adjustments if needed.

 

[Ed]

Well the "whole organo-tin" thing isn't just about killing frogs or fish.. organotins can function with different toxic effects including early embryo death...
Is there a risk, the literature is pretty indicative that there is one. Do we know how much of a risk? I have to say no, as we don't know how mobile it is in the enclosure.. as there is no data showing how firmly it is bonded to the silocone. We do know that it is relased from other polymers like paints used as antifouling agents (see for example

Stebbing A R D (1985) Organotins and water quality - some
lessons to be learned. Mar Pollut Bull 16:383-390 Swain G W, Schultz M P (1996))​

There are some indications that at least some of it may be mobile and if it is mobile then it is getting out into the terrarium at large. See for example, the mobility from solution to substrate in Sorption of Organotin Biocides to Mineral Surfaces - Environmental Science & Technology (ACS Publications) and it should be pointed out that in a number of countries the use of organotins are being banned due to issues with bioaccumulation as it can also be passed up the food chain.

Ed

 

[VivariumWorks]

First of all, the catalyst is a DIbutyltin dialurate. Not a tributyltin. The tributyltin has the potential to do some nasty stuff as you and your reference states, but this is not the ingredient we are discussing. And claiming that tributyltin is an inevitable impurity would be just bad chemistry on the manufacturing company's part considering it wouldn't catalyze the silicone polymer properly, be a waste, and isn't listed on the MSDS and is thereby just speculation.

Then comes the issue that dibutyltin dialurate it is used in surgical/medical grade equipment. That in of itself is enough for me.

Then comes the fact that it is insoluble in water. (hydrophobic) And that it is encased in a solid matrix of a hyrdophobic material. (The silicone polymer.) So water moving over it isn't going to release it to make it bio-available.

Then there is its usage in PVC production. And I see no evidence to stop using PVC in terrariums,vivarium, aquariums, my house plumbing etc...

Then there is its usage in food production as a "de-worming agent" for chickens. And that resins containing it are approved by the FDA for food contact.

So yea TRIbutyltin has potential toxicity issues that are well reported. Dibutyltin dialurate isn't quite as nasty (8 fold less so), has a wide range of uses, and isn't worth fretting over in the context of this usage. Not in comparison to the many other possible toxins/leachate people use in their tanks, like large volumes of calcium hydroxide from improperly cured concrete/grout.

So with no less than thousands of dart-frog tanks built using this material, the fact that its used in fractions of 1%, is bound in a hydrophobic matrix, and is used in materials seen in the hobby since its very beginning (pvc), its just not worth worrying about and especially not worth trying to convince people to purchase a lower grade product that smells much worse.

So again, the "whole organotin thing", in this context and usage, not a believer.

 

[Ed]

If you read through the thread I think I provided links that show that you cannot prevent contamination by other organotins..so it cannot be dismissed as readily...

I provided demonstration that the it migrates out of hydrophobic polymers with citation....

I provided a citation that shows that it does migrate out of solution..

And the argument about small amounts is of little value when we are discussing items that are teratogens, and/or bioaccumulators.. as they can function in very small amounts...

It may not have to be listed on the MSDS if it is registered as part of proprietary information (which is possible if it a contaminent as part of the proprietary manufacturing proccess).

I get your whole premise that you don't believe.. but as a risk this is an easy risk to exclude from the enclosure (simply use one product over another)...

And I should note that I have repeatedly pointed out we don't know whether it migrates in the tanks but it does migrate from other hydrophobic polymers....

Ed