Silicone for new tank rock work

DeCASpecOps

Feeder Fish
MFK Member
May 12, 2013
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Hello all. I'm setting up a new 125 gal tank and I wanted to place a larger rock leaning against the glass to make a viewable cave. I was thinking about using silicone to keep it from scratching the glass and was wondering if I could use any silicone caulk or if it had to be specific aquarium caulk. Any help would be great.
 

Drstrangelove

Potamotrygon
MFK Member
Oct 21, 2012
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San Francisco
Yes, you have to make sure to use 100% silicon with no additives. A lot of brands include a substance to inhibit mold which is lethal to inhabitants if it leaches into the water. I will let someone recommend a specific brand since the makers may have changed the formula, but you do want to be careful. GE used to have one that was popular, but again, make sure you get the right one.
 

PDRed302

Fire Eel
MFK Member
Aug 4, 2011
1,521
90
66
Fort Worth Texas
GE Silicone I, available at lowes, home-depot, ace, etc. It's 100% silicone so it will work great for what you want it for. (give it at least 24 hours to dry)

Make sure not to buy GE Silicone II as it has additives in it (anti-mildew) which can hurt/kill your fish
 

skjl47

Goliath Tigerfish
MFK Member
May 16, 2011
4,404
3,795
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Tennessee
Hello; I have siliconed rocks to glass and rocks to rocks. I found that the rocks need to be dry and to not have a fryable surface. If the surface is prone to be dusty or loose the silicone will pull away bits and the bond will fail..

I also found that giving plenty of extra time for the silicone to cure to be helpful.

One thing to keep in mind when using heavy rocks around glass is that tanks have been reported broken by members. Sometimes by the aquarist dropping a stone and others by fish moving a stone. I believe one member reported the bottom of a tank breaking when a large fish dislogded some rocks in a stack. Perhaps some plastic sheeting to cover the bottom?
 

DeCASpecOps

Feeder Fish
MFK Member
May 12, 2013
50
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Us
Thanks guys the additives were what I was worried about. It's good to know that I can get stuff at the hardware store. They are a whole lot cheaper than aquarium stores.

Sk yeah I was thinking about the glass breaking too. That's why I'm going with a single rock mabey slate. I just want to make sure the top edge doesn't scratch the glass.
 
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