Aquarium silicone sealant comparisons

Ulu

Potamotrygon
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Dec 13, 2018
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I did not read this entire thread but I do have a few comments, having designed with silicone for many years.

I designed systems in which cut stone was applied over steel frames using silicone adhesive and sealant.

I worked as an engineer for a company which manufacturers glass and aluminum glazing, storefronts and aluminum doors. I designed glazing systems which relied on silicone, and there are many high-rise buildings using such systems.

One of the projects I did an engineering study for was the infamous Biosphere habitat. There was a Biosphere-1 and a Biosphere-2 design, and you can look them up online.

It was initially determined that biosphere one was too small and it was enlarged about 25% to create the Biosphere-2 plan. If they had enlarged it by 2000% the project might have been successful.

Like an overstocked aquarium the Biosphere crashed without completing a full cycle. In other words it could never be self-sustaining because too much methane was created inside and not enough oxygen.

Ultimately our company did not take that contract because the client demanded a 100-year guarantee on what is essentially a glass, silicone and aluminum dome, applied over a welded steel frame.

You will find that the project failed and was closed out long before the 100-year guarantee, not because the silicone leaked, but because it was so tight there was Zero air exchange and the people inside were suffocating.

To be honest, it was supposed to replicate a habitat on the surface of Mars, so the entire thing was glass but you could not open a single window.

They were trying to test a totally sealed dome environment with people, animals and crops inside.

But just like an aquarium, it was the bacteria to be the downfall! As they broke down organic matter and wastes, gases were created that could not be contained or dealt with, and certainly not breathed.

ANYHOW . . .

GE Silicone-1 was specified and normally this came with a 20 year guarantee, though over the years that guarantee was increased to 25 and then 30 years. But this client demanded a 100-year guarantee and General Electric signed that, with provisions including that there was a full-time on site continuous inspection of the cleaning and sealing.

Accelerated aging tests had been done in the past, which convinced General Electric that they could offer this to a particular client under a particular situation.

Of course every engineer involved in the project knew that it would not run anywhere close to 100 years. For the University to get funding for just a two-year program was nearly impossible.

Cleaning is a vitally important in this business if you want a seal that lasts a long time. It is in fact the most important part of the entire business.

I have one new tank sealed with GE SCS and one I resealed with GE Silicone-1. It was only done one year ago so no guess on the long-term durability of my repairs. The SES tank was done at the same time.

Anyhow GE Silicone-1 is the thing to use in my mind. I'm sure you can spend more money but I don't think you can buy better as it is pure 100% silicone.
 
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fishguy1978

Redtail Catfish
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Mar 30, 2020
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I wish I had come across this before use DAP 08646 to seal some glass hole covers on the bottom of my 220. I emailed DAP to ask why the 08646 is not suitable for submersion and was told that it will lose adhesion, eventually. How long? I will let you know.
 

Toby_H

Polypterus
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Jun 21, 2007
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I’ve been out of the DIY Aquarium world for 10 years or so. As I get back in, I’m reviewing a lot of old information to see what’s changed.

I’ve used GE Silicone 1 on many projects in the past, but when I went to get some recently, I saw it was “7 year mold free”, which to me means “not aquarium safe”.

I went to several local Hardware stores and they all stocked this new “mold free” version of Silicone 1. When I looked around online, some places posted (what I assume to be) older photos that do not say “mold free” and others have (what I assume to be) newer photos that do say “mold free”

Can anyone clue me in on details related to this change?

Here is a link to Lowe’s which has a 360* View so you can read the back labels if interested.

https://www.lowes.com/pd/GE-Silicon...bQmICCV-INIpykpLLi8aAszaEALw_wcB&gclsrc=aw.ds

Here are photos which include “Silicone 1” and “7 year mold free”
GE Silicone 1.png
 

Rocksor

Blue Tier VIP
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Nov 28, 2011
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I’ve been out of the DIY Aquarium world for 10 years or so. As I get back in, I’m reviewing a lot of old information to see what’s changed.

I’ve used GE Silicone 1 on many projects in the past, but when I went to get some recently, I saw it was “7 year mold free”, which to me means “not aquarium safe”.

I went to several local Hardware stores and they all stocked this new “mold free” version of Silicone 1. When I looked around online, some places posted (what I assume to be) older photos that do not say “mold free” and others have (what I assume to be) newer photos that do say “mold free”

Can anyone clue me in on details related to this change?

Here is a link to Lowe’s which has a 360* View so you can read the back labels if interested.

https://www.lowes.com/pd/GE-Silicon...bQmICCV-INIpykpLLi8aAszaEALw_wcB&gclsrc=aw.ds

Here are photos which include “Silicone 1” and “7 year mold free”
View attachment 1453353
The 7yr mold free is new. Although in the last 6 years or so, the instructions have stated that it GE Silicone I is not aquarium safe.
 

Ulu

Potamotrygon
MFK Member
Dec 13, 2018
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Yes it is definitely not as safe and you should also be careful about buying older stock of the GE silicone 1 that was not mold repellent.

I have a few tubes left and one of them turned out to be defective and it would never cure. This stuff has a shelf life and it can vary depending on the conditions on which it has been stored.

Anyhow the days of buying aquarium silicone at Lowe’s are over I guess. I’m going to have to complain to them about this.
 

Backfromthedead

Potamotrygon
MFK Member
Jul 12, 2017
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Fredericksburg va
Been using black dow corning 795 with good results but I'm switching to clear scs1200 for a couple of new builds, see how that works out. I order off of amazon for the convenience and price.
 
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