Strong silicone

[sumpnfishy]

I've been looking for a thread that talked about a sealant that works for large tanks. I've resealed my 225 gal tank 2 times, only to have it leak again within 6 months (different areas). I've been using the GE 100% silicone which works great on other tanks. I read here some time back about a stronger version that works better for large tanks but now I cannot find it. I think someone said it was RTV 108.

Anyone know what works best for tanks that size?

The tanks been sitting empty for 6 months now and I want to get it up and going again...

Thanks

Dennis

 

[barterking85]

a good silicone is a good silicon there is no bond strength i like the use 100% silcone aquarium safe from home hardware but if ge has worked on your other tanks it dosent matter the size it will still work. imo

 

[BillD]

If you are getting leaks from a reseal, it isn't the silicone that is the problem. You need to look at your procedure. I would suspect that you are leaving trace amounts of the old silicone. There are stronger silicones such as GE 1200 series (possibly the RTV also, but I'm not sure). This would be desirable in the building of a large tank. The 1200 series is meant for contractor use and isn't normally seen in stores that don't service the trades.However, a reseal doesn't require the strength of a build as all it does is provide a seal without adding to the structural integrity. Any silicone should work for that. The one thing I always do, once I am positive I have removed all the old silicone is to get a new blade and go over it all again, sometimes twice. After that, a good cleaning with acetone or alcohol to remove any traces of skin oils or other residue. It is imperative that you do not touch the area to be siliconed with your hands. A pair of nitrile gloves my be a good idea to avoid any risk. In addition I like to extend the new silicone beyond the old bead in order to contact virgin glass. This isn't always possible if the previous bead was sloppily applied.
One thing that is never mentioned is application technique. You want to lay the silicone in with no voids in it. This means careful application of the bead and forcing it into the vee with no air inclusion. This sounds simple but does require some consideration, as you don't want to "drop" it in. If you are new to caulking or not really comfortable with it, (this tip from another forum) you can practice on a cardboard box with any cheap caulk to get the feel for it. The other thing is that an overly large bead is of no benefit and is more difficult smooth cleanly, which is important to ensure good contact on the edges of the fillet. if the edges are not clean and tight there is the risk of water starting to get under the silicone at those points.
I surmise you are not a total beginner when it comes to this, so examine your technique. The one thing that would concern me is that you mention the tank leaks from different spots. It sounds like the initial build was sloppy. A well assembled tank will hold water without the inner seal.
Regardless, don't give up. Almost all my tanks came to me as leakers and I am still using one I built in the mid 60s.

 

[sumpnfishy]

It is a very old custom built tank that came from a school years ago. The support frame was missing so I rebuilt that with various plastic and aluminum parts. I do use several blades and clean with alcohol before adding new silicone. I do a lot of DIY work on my homes over the years so I do have a lot of experience with calking / sealing.

It held up fine for about a year then last fall I had several leaks over the course of few months so I gave up.

I've ordered the GE RTV 108 on the Internet so hopefully that will do the trick. Of course you don't really know until several months have passed if it's fixed. Luckily this in my fish room in the garage so it is mainly an aggravation when it does leak.

I'll post an update after I've tried the 108.

 

[barterking85]

ok cool any silicone is great as long as its aquarium safe and a clean smooth bead is always better then a thick sloppy one but i would still have to say one silicone dosent have a stronger bond then another imo iam a carpenter i do mainly kitchens and bathrooms so i do silicone up the wazoo. If you have the time and patience it might be worth it do redo the inner seams too then your mind will be clear anyway your choice let us know how it goes

 

[BillD]

The bond strength of GE 1200 series silicone is higher than GE I.

 

[barterking85]

i mean like if you use silicone insted of pl 400 to hold a back splash on i dont care what kind it is its not gonna hold and the only difference between the two silicones is ge 1200 is USDA and FDA approved which means you can use it where food is prepared and stored cause it dosent leach

 

[BillD]

The difference between the two silicones is the bond strength. If you were building a large tank, why wouldn't you use the strongest?

 

[barterking85]

ok whatever man iam just a carpenter who uses silicone everyday and has talked to the reps but what would i know if it puts your mind at rest use it

 

[xxwolfpackof1xx]

no arguein guys we all have opposing opnions and know more or less the others keep it civil and on topic to help the OP

 

[barterking85]

yeah i know just gets to me sometimes appoligies BILL got a little worked up

 

[xxwolfpackof1xx]

yeah i know just gets to me sometimes appoligies BILL got a little worked up

its ok it's bound to happen we all have opposing views opnions and info i jst dont wanna see a fight here in the thread and for a mod to repremand you so stay positive helpful and happy

 

[BillD]

No problem Ryan. The info is available on the GE site. 1200 series isn't necessary for most jobs, such as caulking around the house or an aquarium reseal, there are jobs where it would be preferable. I believe it has a higher shear strength also, which would be advantageous in a large tank. Large tanks are built with thinner glass than they were years ago, so bond and shear strength are more important than they were. I am told that the major manufacturers use the 1200 series, but I can't verify that.