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Discussion Starter · #1 ·
This is a thread detailing how to repair a cracked viv. I have 20 plus years working with glass professionally.
I was recently given several brand new Euro style vivs with sliding front doors. They were given to me because they had cracked bottoms. They are otherwise in perfect, brand new condition so were well worth repairing. The first 4 will fill up a rack for me as these are very nice sized vivs. They measure 22.5" x 17" x 24" tall pushing almost 40 gallons each. Perfect 4 pack for a bakers rack. The final one will be my ultimate viv. It is a 70ish gallon corner display viv measuring 2 ft x 2 ft x 3 feet tall! I just got a group of 6 Southern Variabilis that should feel quite at home when I am done.
Let's start with a photo of the cracked bottom. I have turned the viv over for easy acess.
 

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Discussion Starter · #2 ·
As you can see, this is a frame-less viv. If yours has a frame, you will have to slice it off first. I would do this with a very thin, flexible, putty knife. I use a flexible putty knife like this to separate windows from the frames. If you use a tin snips to round the end of the knife, it will slide through much easier because the corners won't catch. Pic shows how the tool starts out and how it looks after cutting the corners.
You will have to run the putty knife several times all around the trim. Once it is removed, the rest of the job will go just like mine.
 

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Discussion Starter · #3 ·
I tried the guitar string method I've read about but the bottoms were much too tight. I got it to slide in about an inch before it began pinching the string and broke it. I ended up cutting them away with razor blades. You are going to want PLENTY of razor blades for this job.
The first step will be to reach inside and cut through the "filet" or bead of silicone from the inside. I chose to leave the viv upside down and reach on through the front doors. On a more conventional tank you will flip it right side up first.
Run the blade all the way around the bottom. It may take a couple passes but cut until you feel the blade hitting the glass.
 

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Discussion Starter · #4 ·
After this is where it starts to get a little more difficult. You are going to try to slide your blade in between the cracked bottom and the bottom edge of the glass. In some spots, it may cut in fairly easily. Where it does, just keep running that blade along the edge, cutting it away. If you are really lucky, you can just cut the whole bottom away that way.
 

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Discussion Starter · #5 ·
I wasn't so lucky. As I said, these vivs were glued very tightly. I used several tricks to keep the blade cutting. When it got too tight, I slipped a second blade in behind the first one. This helped lift the glass a little bit, like a wedge, relieving some of the pressure on the first blade.
Remember to keep replacing your blade as it dulls and chips quickly during all this.
 

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Discussion Starter · #6 ·
Eventually, I hit spots so tight that would not work either. I found that heating the glass with a hair dryer helped to make the silicone rubber just a little more flexible. Make sure you are only heating the cracked bottom pane.
 

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Discussion Starter · #7 ·
Still, I had spots where the blade would go no further. At this point, I held the blade with one hand and gently tapped the blade forward with a small hammer. You have to be careful not to hit the edge of the glass and also be careful not to let the "rib" of the razor blade hit the edge. You want just the skinniest portion of the blade slicing through.
Usually, after forcing the blade through for a half inch or an inch, I could continue slicing by hand.
 

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Discussion Starter · #8 ·
In some of the tightest areas, I did get some chipping, but only of the already damaged piece.
 

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Discussion Starter · #11 ·
With the bottom lifted, slip the corner of the blade into the last bead of silicone and "rock it" straight in, cutting through the bead.
 

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Discussion Starter · #12 ·
Repeat this step, till you've worked your way all along the last edge. (This is all done from the inside as you are lifting the pane, thus opening the gap on the inside edge, but making it even tighter on the outside edge.)
Once you've worked your way all the way down, you'll feel it just lifting away and with one simple slice, the bottom is completely removed.
 

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Discussion Starter · #13 ·
Fresh silicone does not stick well to old silicone so you must scrape off all you can. I chose not to use silicone removers as they could compromise the edges, and I don't like using mystery chemicals on something my frogs will be exposed to. Instead, I used my Random Orbital Sander with 80 grit sandpaper. It really made short work of EVERY LAST BIT of silicone from the bottom edge. Here, you can see some pictures of what it looks like when you begin sanding. Once you start sanding, it becomes very obvious where there is still silicone stuck. These pictures show areas that are NOT good enough yet.
 

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Discussion Starter · #16 ·
Wipe it down with a damp rag, use several blades to remove traces of silicone still on the faces of the glass. One last quick wipe-down with some rubbing alcohol.
Here you can see how I like to "notch" my silicone tube. This notch helps me to guide the bead exactly where I want it.
I use GE silicone 1. I don't use GE 2 because of the organotins in it. http://www.dendroboard.com/forum/parts-construction/35720-bio-seal.html
 

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Discussion Starter · #17 ·
Once your bead is complete you gently lower your new pane onto the inverted viv. This is easiest with two people. Grab some masking tape and tape it in place.
After it is taped in place, you'll want to reach inside and smooth out your bead. There are tools for this but I hate them. I just use my fingers and plenty of paper towels.
Give it 24 to 48 hours before removing the tape.
I'd show you the completed vivs, but they are drying! ;)
 

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Great write up.

One question I had because it is a bit hard to tell from just your picture, but are you putting the bead of silicone on the edges of the existing glass of the tank, or on the new piece of glass? I'm guessing your putting it on the edges of the tank glass, at least I think thats what I'm seeing in the picture, you use the little notch to stay on the edge of the glass?

Another question, any recommendations on minimum thickness of glass to use? I know that the size of the tank and how much weight you'll have in the tank (filled with water or not) would change things, but got any general rules to follow?

Thanks for putting this together, I've got a 30 gal long laying around with a broken end pane. Maybe this will motivate me to finally do something with it. ;)
 

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Good job with the post and "how-to" Pumilio. Thanks.

Great looking corner viv, too. What a score for you!

-Troy
 

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Discussion Starter · #20 ·
Good job with the post and "how-to" Pumilio. Thanks.

Great looking corner viv, too. What a score for you!

-Troy
Thanks Troy, wait till you see it completed! I've been saving up the choicest pieces of ghost wood and cork bark with a bunch more on the way.

Great write up.

One question I had because it is a bit hard to tell from just your picture, but are you putting the bead of silicone on the edges of the existing glass of the tank, or on the new piece of glass? I'm guessing your putting it on the edges of the tank glass, at least I think thats what I'm seeing in the picture, you use the little notch to stay on the edge of the glass?
You've got it exactly. Silicone on the existing edges, using the notch as a guide. The new glass goes on clean (no silicone).

Another question, any recommendations on minimum thickness of glass to use? I know that the size of the tank and how much weight you'll have in the tank (filled with water or not) would change things, but got any general rules to follow?
That's too easy. Copy the size the manufacturer used. Mine were built with 1/4" so that's what I went with.
When I build from scratch, I use 1/8" for my vivs up to 25 gallons. This is rather thin but it's free scrap glass so I use it. With only the inch or so of water under the false bottom, they work fine as long as I'm careful. I step up to 3/16 for my 24" x 24" x 24" 50 gallon size slope fronts. If I were purchasing glass instead of the free scrap I get, I would step up to 3/16" for my 25s and 1/4 for my 50s.

Thanks for putting this together, I've got a 30 gal long laying around with a broken end pane. Maybe this will motivate me to finally do something with it. ;)
Good luck with it!
 
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