Do I replace existing silicone?

[Bedard1]

Hi everyone! I'm new here and hope I have posted in the right place, if not please point me in the right direction.

I was just given a used 90 gallon tank and had a few concerns. Some of the silicone within the tank is 'thin', 'worn down' and possible even missing from one of the corners in the tank. It even seems as if there is algae or dirt stuck under the silicone (is this a problem?). I filled the tank completely to the top and left it there for 3 days in order to check its reliability. After the 3 days there were no signs of leakage, etc.

My concern is that what will happened when I have the tank full and with sand/decorations after an extended amount of time, will the silicone become problematic than? I know the tank was used for a good amount of years and was empty and 'stored' inside a house for at least 3-4 years. Could this have negative effects on the silicone? I know people who have stored there tanks outside in a shed for a year or two and it was exposed to heat and cold, the tank given to me however was inside with a stable temperature.

I would prefer not to replace the old silicone, so I was thinking since there is no leak I would be able to just apply new silicone over the existing silicone. I was thinking of using ASI Aquarium Silicone Sealant (http://www.americansealantsinc.com/a...arium-sealant/) or RTV 108 Silicone Sealant (http://www.newark.com/momentive-perf...tube/dp/00Z645). Would this be an option? If so, would either of these silicone's work when applied to existing silicone? If this won't work, what are my options?

I will attach some pictures to help determine what I should do. The silicone in the picture of the side of inside the tank is a little under the width of a pencil (picture won't load).

Thanks in advance!

[MrGuy]

Welcome- I'm a newbie here also, but not a total aquarium newbie. I can weigh in on this and say definitely YES replace all the silicone. It is time consuming and may also cause you to get out the band-aids a few times, but you must replace all the silicone visible on the the glass.

I would watch the "King of DIY" video on youtube about replacing the silicone because he shows (in my opinion) the most comprehensive way to do it.

I just did a 75 gallon myself and the hardest part is scraping all the silicone off with razor blades. The actual applying the silicone is easy. I used rubbing alcohal over and over again when I think I had it all and then gently ran my fingers over all the edges. Just when you think it's all gone, there is more that you need to scrape over again with the razor blade.

Also, buy a lot of razor blades...they dull surprisingly fast.

Here is the link to the youtube video, but you can find many good ones to help you.
https://www.youtube.com/watch?v=D_Meyb2JYCU

[MrGuy]

Oh and you can also save some cash and use GE Silicone I (ONE), Never TWO..because that has fungus/mold inhibitors that are no good for marine life.

[Sandy Cheeks]

I think you don't have to remove the bonded edge's silicon "seam"? unless you are re-building the whole tank. Just the silicon on the corners.
Is a PITA to remove it bu you sure can do it. 100 pack of single edge blades from HD more than enough and plenty to spare for future cleaning of the glass when the tank is running.
When applying silicon, you have the option to put painter's tape so you can get an even and nicely straight bead of silicon. You can also use an old gift/credit card with a rounded corner to spread it nicely. Have plenty of paper towels and lots of ventilation.
Good luck.

[JonezNReef]

Don't put new silicone on old because they wont bond together. Trust me from experiance I have found out that taking short cuts or saying something will work for now never works in this hobby. Not only do you regret it later on but you also spend more money in the end. And the last thing you want is a tank blow out.


When I redid my 180 I removed all silicone one the inside the of the tank and was careful not to hit the structrural bonded silicone between the two panes. I removed it with razor blades and rubbing alcohol. After I removed the silicone I did a leak test to see how good the structural seam was. I figured if it could hold water without the inside silicone then I had nothing to worry about. After it passed the water test me and a few others tag teamed the inside silicone with ease with one siliconing, one smoothing and the other pealing the tape.
There is a lot of good info on this site and the internet which I recommend using.

[stelliofleondis]

90 gallons of water on the floor is a way bigger headache than scraping off and then replacing a little silicone. Truth be told that is one lesson you don't want to learn the hard way. plus dead fish and corals will cost you big time.

[ca1ore]

There are many threads on this. The silicone between the glass panels is what maintains the structural integrity of the tank, so simply replacing the internal 'seal' does NOTHING to reduce the chance of tank failure. If a tank leaks, it means the structural seal is compromised and it should either be discarded or pulled apart and rebuilt.

I don't think there's a topic here on RC with more misinformation than this one.

[GimpyFin]

Originally Posted by ca1ore

There are many threads on this. The silicone between the glass panels is what maintains the structural integrity of the tank, so simply replacing the internal 'seal' does NOTHING to reduce the chance of tank failure. If a tank leaks, it means the structural seal is compromised and it should either be discarded or pulled apart and rebuilt.

I don't think there's a topic here on RC with more misinformation than this one.

I agree with this.

Examine the seams in between the panes of glass. If those aren't compromised, then the tank should be fine. The extra silicone on the inside being a little light/uneven in spots or some crud buildup there won't affect whether the tank will leak or not.

[davocean]

^^ Agree w/ last couple posts and also agree too much misinformation given here, new silicone will not bond to old, so much so that even the slightest residue of old will keep it bonding in that area, meaning it does nothing.
People who reseal take the tank completely apart, and go to great length's wiping w/ rubbing alcohol numerous times so there is not even a hint of the old silicone left.
It's a much harder task to reseal a tank than most would think.

[tweetyfish]

Originally Posted by JonezNReef

Don't put new silicone on old because they wont bond together. Trust me from experiance I have found out that taking short cuts or saying something will work for now never works in this hobby. Not only do you regret it later on but you also spend more money in the end. And the last thing you want is a tank blow out.


When I redid my 180 I removed all silicone one the inside the of the tank and was careful not to hit the structrural bonded silicone between the two panes. I removed it with razor blades and rubbing alcohol. After I removed the silicone I did a leak test to see how good the structural seam was. I figured if it could hold water without the inside silicone then I had nothing to worry about. After it passed the water test me and a few others tag teamed the inside silicone with ease with one siliconing, one smoothing and the other pealing the tape.
There is a lot of good info on this site and the internet which I recommend using.

I did the same as this post on my Oceanic 180. Removed all except the structural bond and replaced with new. Came out looking great and using a good adhesive silicone helps with keeping containments away from the silicone between the panes of glass.

[mickey204]

Originally Posted by davocean

^^ Agree w/ last couple posts and also agree too much misinformation given here, new silicone will not bond to old, so much so that even the slightest residue of old will keep it bonding in that area, meaning it does nothing.
People who reseal take the tank completely apart, and go to great length's wiping w/ rubbing alcohol numerous times so there is not even a hint of the old silicone left.
It's a much harder task to reseal a tank than most would think.

Bang on.

I've built numerous silicon & acrylic tanks and if you want to repurpose a tank (which is fine) because it only costs your time & silicon + solvent cleaner to clean the tank then you HAVE to fully clean all the silicon off.

Razor blade, wipe, razor blade, wipe.

https://www.youtube.com/watch?v=2YlaC8SCHb8

[Lsufan]

If it's not leaking then I don't think I would mess with it, if it is leaking I would give it to someone for a terrain tank or put it to the curb. There's to much effort in rebuilding a tank if it has a leak.

Like calore & Dave mentioned, it's the silicone between the panes of glass that is the structural seam on a tank. So if a tank leaks then the structural seam is compromised & the tank would have to come completely apart. The inner seal is really there to protect the seal inbetween the panes of glass.

Being u say it isn't leaking I would recommend leaving it alone, u may do more harm then good if u compromise the structural seam in the process. U can replace the inner seam but it will mainly be for cosmetics & u will have to be careful not to mess up the seam & get every bit of silicone off & have the glass cleaned to where it's like new. Be careful watching some of those u tube videos because they have quite a few that may get u in trouble.

As far as silicone, RTV 108 is what I usually use.

[JacksonAction]

If you have never worked with silicone before I would recommend leaving it the way it is. It's easy to work with but it's hard to get your seems to look nice if you're not experienced with silicone. It's not like your bathroom tub where the silicone blends in with the wall and no one pays attention to it. In an aquarium, mistakes and smudges will be noticed. Let us know about your experience if you decide to do it and post some after pics. Good Luck

[Bedard1]

Hello everyone! Thank you so much for all of your input, I inspected the tank further and noticed it must have been slightly hit on the side due to it having a small chip between two pieces of glass. But I noticed the chip had caused the inner seal that keeps the two pieces of glass together had been shifted to some extent. There are a few bubbles where it serperated from the other piece of glass and now I am reconsidering everything once more. Despite it being able to hold water for 3 days I do not trust this small separation between the two pieces of glass. Attached are a few pictures (Please zoom it to better see the chip/bubbles) of what I am trying to describe. Should I try and fix it, just use it, or trash it, or even sell it and let the buyer know that it needs to be fixed? Thanks again everyone!! =))

[ca1ore]

It is not unusual to have bubbles in the silicone, doesn't mean there's been separation. Further, light will reflect differently through the chipped area and may throw shadows that mislead. Hard to say what you should do though. Personally, I would not use a tank that showed glass/seam damage. Further, the cost of a new tank would dissuade me from the tedious job of dismantling, cleaning off all the old silicone and reassembling. Got PitA written all over it.

[davocean]

Just going by what I see in those pics it looks like just a surface chip and most likely no big deal, I've had and seen many tanks that had similar, but bottom line you see it better than we do and gotta go w/ your own gut.

I agree, sealing a tank is a pain beyond what I'd want to deal with, and when it comes down to it the actual glass part of all your investment is nothing compared to the cost of everything else that goes in and below that glass.

[Skippy2512]

Great post. I just picked up a used tank and was wondering about this same thing. Thanks for the posting!


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[uncleof6]

Originally Posted by MrGuy

Oh and you can also save some cash and use GE Silicone I (ONE), Never TWO..because that has fungus/mold inhibitors that are no good for marine life.

As a tank builder I cannot recommend using GE Silicone I for any aquarium purpose. This silicone is a bargain basement extreme low end material, and the cost savings is a pittance in comparison to the actual cost of this hobby. Alternatives are made by Dow Corning DC 999A, DC735, and the like. Aqueon's branded silicone is a Dow Corning product.

There are no mold/fungus inhibitors in GE Silicone II. According to the published information on this product, there are no additional ingredients (proprietary or otherwise; disclosure required by law.) that are mold/fungus inhibitors. The formulation is consistent with any other neutral cure silicone on the market. The issue with GE Silicone II and all other neutral cure silicones is the end user failing to allow sufficient cure time. Although all silicone is toxic unless fully cured, Acetoxy cure silicone is less toxic that neutral cure silicone. 24 - 48 hours is insufficient cure time for the way, manner, and amount of silicone used in this hobby.

[Lsufan]

Originally Posted by uncleof6

As a tank builder I cannot recommend using GE Silicone I for any aquarium purpose. This silicone is a bargain basement extreme low end material, and the cost savings is a pittance in comparison to the actual cost of this hobby. Alternatives are made by Dow Corning DC 999A, DC735, and the like. Aqueon's branded silicone is a Dow Corning product.

There are no mold/fungus inhibitors in GE Silicone II. According to the published information on this product, there are no additional ingredients (proprietary or otherwise; disclosure required by law.) that are mold/fungus inhibitors. The formulation is consistent with any other neutral cure silicone on the market. The issue with GE Silicone II and all other neutral cure silicones is the end user failing to allow sufficient cure time. Although all silicone is toxic unless fully cured, Acetoxy cure silicone is less toxic that neutral cure silicone. 24 - 48 hours is insufficient cure time for the way, manner, and amount of silicone used in this hobby.

That is one of those myths in the hobby that I don't think will ever go away, but hopefully every time someone states that it's a myth a few more people catch on. I know people are trying to help but I see this all the time when people talk about silicone.