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Discussion Starter · #1 ·
I need to finish a few products for my build. And there are a few things I really need help with. I'm frankly just tired of thinking about it and I would like to know what others think or would do. I'll list my current issues, but I'll probably have to add some as I go.

1) My tank was used for a reef so it need a thorough cleaning, but I think the previous owner used a razor blade for coraline removal. The silicone in the corners is nasty with stain and algae and heavily lifted. The edges are all jagged and torn down to the sand level. The rest of the silicone is young (less than two year old tank) and looks fantastic. It simply seems the edges of the corners are toast from cleaning.

2) The overflow is a peninsula style. It is centered in the center of one end of the tank. It is also very large, probably 10" x 7" or so, so I loose a lot of space. I want to redo this.

3) Combining the two issues above, I want to cut a slot for a weir at one end of the tank and then add an external overflow. I think it will look great and clean, plus I get about 5 gallons back. If I redo the silicone, the internal OF can be cut out without issues because I will reseal the inside to fix my silicone problem.

4) How do I cut the slot for the weir? I would be doing it myself but I don't know what do use. I basically want to do it right and keep the risk down. This tank is beautiful and I don't want to rebuild it.

5) I will have holes left from the current OF. I can plug them and use a MP20 for flow, or add a closed loop. I don't have the powerhead, but I have the pump for the loop. Both have their positives and negatives, but I'm thinking the vortex is a better way to go, but the CL could be really cool too.

Let me know what you think. Feel free to throw me comments on any issue. I just want to discuss some of this stuff and figured I'd do it all in a single thread.

Thanks.
 

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We can start with the fact that you can't just cut a section out of a glass tank.

If you start removing silicone, to reseal, remove it all and do the job right the first time. Silicone will not bond to old silicone. Scrape it all off and seal it all. Use silicone labeled for aquarium use. Yes, there are some cheaper alternatives that may work, but is it really worth the possibility that you'll have to tear it down, re-scrape and reseal with the correct product?

Depending on where your left over holes will be you may be able to silicone glass over them and save the cost of bulk head plugs.
 

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Discussion Starter · #3 ·
We can start with the fact that you can't just cut a section out of a glass tank.
Oh boy. Check out this thread here. And this one here. Maybe you didn't know what I meant?

If you start removing silicone, to reseal, remove it all and do the job right the first time. Silicone will not bond to old silicone. Scrape it all off and seal it all. Use silicone labeled for aquarium use. Yes, there are some cheaper alternatives that may work, but is it really worth the possibility that you'll have to tear it down, re-scrape and reseal with the correct product?

Depending on where your left over holes will be you may be able to silicone glass over them and save the cost of bulk head plugs.
I will be using RTV108 to reseal. It's pure and waaaay stronger than GE or similar products. I will be scraping off all the silicone in every corner, but leaving the seams holding the tank together intact. Is that what you mean?

I'm going to plug the holes with bulkheads (already have them) if I don't do a close loop. I'm tore between the loop and the Vortex powerhead though.

Keep in mind I've researched these things to death, I'm just indecisive and need some guidance/ opinions.
 

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The best idea I've seen for cutting glass was the use of a Dremel tile cutter bit. The poster bought a few of them, set the glass horizontally, drew a circle for their bulkhead cut, built a short water barrier around the cutting area out of putty and added a bit of water for cooling, drilled a hole straight in then followed around their circle. This avoided the chipping that always happens on the back side when using a hole saw. Sounds like it might be ideal for your plan. Honestly if you want it done right you might want a glass pro to do it, but then if they break it....
 

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If the original overflow bulkheads were in the floor, I would use loc-line on them for the in/out of a closed loop, then hide them behind plants and hardscape. Tom Barr did this for the main filtration on some of his tanks, I like it because it gets rid of ugly filter pipes, something I plan on using if I ever get a rimless. The inlet would actually have a grate over it then the outlet would have a short loc-line so you can point it in any direction.
 

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Discussion Starter · #7 ·
If the original overflow bulkheads were in the floor, I would use loc-line on them for the in/out of a closed loop, then hide them behind plants and hardscape. Tom Barr did this for the main filtration on some of his tanks, I like it because it gets rid of ugly filter pipes, something I plan on using if I ever get a rimless. The inlet would actually have a grate over it then the outlet would have a short loc-line so you can point it in any direction.
Exactly what I was thinking. But I'm wondering if the vortech would be better than a closed loop.
 

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We can start with the fact that you can't just cut a section out of a glass tank.

If you start removing silicone, to reseal, remove it all and do the job right the first time. Silicone will not bond to old silicone. Scrape it all off and seal it all. Use silicone labeled for aquarium use. Yes, there are some cheaper alternatives that may work, but is it really worth the possibility that you'll have to tear it down, re-scrape and reseal with the correct product?

Depending on where your left over holes will be you may be able to silicone glass over them and save the cost of bulk head plugs.
easily available "aquarium silicone" is crap get an industrial silicone that is water safe, I believe scolley found a silicone that would work, the common aquarium silicone is like ge window and door silicone 2.
but the above comment is correct if you plan on adding any silicone remove ALL of it and re do it, but do it with a damn good silicone or you may end up regretting going the cheaper route
 

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also I would try doing a beananimal overflow if at all posible, witnessed one, the guy who had it tried to cause a flood but he was unable to even cause one without clogging the pipes which is easy to avoid also, not to mention i couldnt even here moving water...
 

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Discussion Starter · #10 ·
When you guys say "remove all the silicone" do you literally mean ALL of it? Cause then I only have 5 pieces of glass and I will have to rebuild the tank.

What I am planning is cutting out the corner bead and leaving the seams that actually hold the tank together. I will remove every scrap and film of old silicone up to the joint and clean it with denatured alcohol. Then I will redo the corners with RVT108. It is industrial strength silicon. Much better than GEll or other commercial grades.

Just a cool little factoid, while GEll and the like don't stick well to dry silicone, rvt108 will stick better to itself than glass. I thought that is kinda neat. You have to work really fast with it though, cause it skins over quickly and it Hella strong.
 

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I believe they mean the beads in the corners only. The thin layer between the glass is what's doing all the work, I wouldn't touch that. I have been removing the corner beads forever and do not replace them with new silicone, people I know think I'm stupid, they just can't understand how silicone works no matter how many times I explain tensile and shear force to them.
 

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Oh boy. Check out this thread here. And this one here. Maybe you didn't know what I meant?
You're right, I didn't know what you meant. Or that there were people insane (in a the meaning of the term) enough to cut slots in a glass tank.

I will be using RTV108 to reseal. It's pure and waaaay stronger than GE or similar products. I will be scraping off all the silicone in every corner, but leaving the seams holding the tank together intact. Is that what you mean?
Yes, leave the glass stuck together, but replace all the silicone inside the tank. Doing just the sides is asking for leak later.

As for the post later about cutting out the inside silicone and not replacing it, the poster is braver about water than I am.
 

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Discussion Starter · #13 ·
I believe they mean the beads in the corners only. The thin layer between the glass is what's doing all the work, I wouldn't touch that. I have been removing the corner beads forever and do not replace them with new silicone, people I know think I'm stupid, they just can't understand how silicone works no matter how many times I explain tensile and shear force to them.
Personally I wouldn't leave it out unless I knew what was used originally, but that's just me. If cheaper silicone is used I'm sure it adds a bit of strength to the seam as a whole, although I understand it the shear force that is critical. If a good product is used in the first place they don't need the corner bead.

also I would try doing a beananimal overflow if at all posible, witnessed one, the guy who had it tried to cause a flood but he was unable to even cause one without clogging the pipes which is easy to avoid also, not to mention i couldnt even here moving water...
I will be going beananimal for sure. My system will be slightly different but the basic idea is the same. I will be keeping the water level quite high in the box to minimize turbulence. I will be running a co2 system and want to keep the gassing off down.

You're right, I didn't know what you meant. Or that there were people insane (in a the meaning of the term) enough to cut slots in a glass tank.
You know... I agree with you completely. It's totally nuts, but I think I might be crazy enough to try it. I think if I set it up properly I could pull it off.

This doesn't really support my cause, but today I took a POS dremel tool (a cheap copy brand) and a crap diamond coated cutting tool from one of those cheap multi kits and tried cutting a chunk out of a tank. It was ancient and all beat up so I'm tearing it apart anyway. It had 1/4 glass and I got about 1cm in from the edge before I snapped a piece off. I made a few more cuts before packing it up. Even for a garbage tool and bit it cut easily. I think the reason I chipped the tank was because I was free-handing it and testing out how much pressure and rpm worked best. I was really hammering on it. If I get a rotorzip and a template I think it would work okay. I might also explore using a rotor with a special bit.
Yes, leave the glass stuck together, but replace all the silicone inside the tank. Doing just the sides is asking for leak later.

As for the post later about cutting out the inside silicone and not replacing it, the poster is braver about water than I am.
What do you mean by "doing just the sides is asking for leak later"? I'm not following that bit. I'm only going to do the inside corners.

In all seriousness, what do you think about cutting the slot/ weir into the tank.
 

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What do you mean by "doing just the sides is asking for leak later"? I'm not following that bit. I'm only going to do the inside corners.
Some people try to remove and reseal only the vertical corners of the silicone leaving the horizontal bottom beads. Since new silicone won't bond to old silicone, there is a possibility of water seeping into the joint where old meets new and leaking. So, scrape and reseal all eight places where glass meets glass.
 

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Discussion Starter · #15 ·
Some people try to remove and reseal only the vertical corners of the silicone leaving the horizontal bottom beads. Since new silicone won't bond to old silicone, there is a possibility of water seeping into the joint where old meets new and leaking. So, scrape and reseal all eight places where glass meets glass.
Oh, yeah. Makes sense now. Thanks for clarifying.
 

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All the work really is being done in the main seam where the edge is flushed against the larger pane. I had 1/2 glass in one so a lot of strength in that joint. I think the corner bead is mainly placed to avoid seepage into air bubbles left in the main seam. I have never removed silicone from a new tank or one with beads in solid condition, I figure if the whole corner is shredded and growing algae underneath, it's not doing much for seepage anyway. The only tank I've ever sprung a leak on was ancient, chipped corners, and there was a visible gap underneath in various places where it should have been placed on foam support (stand started sagging), out of level, bad setup all around but leak tested well for over a month and took a couple years to develop a leak. I don't think I ever removed the bead in that one but it was shredded and nasty green/ brown underneath. I think the support of the tank being shifted in weird directions is far more dangerous than missing or damaged corner beads. If you think of having your finger and thumb siliconed together, it's easier to slide them back and forth to separate them than it is to pull straight apart. the corner bead has no way of utilizing this property seeing as the bonded sides are perpendicular rather than parallel.
 

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Discussion Starter · #17 ·
Okay, I just had an idea that is probably less insane than slotting the glass. Right now the aquarium is eurobraced and built with 12mm glass. All the glass thickness calculators I can find say this gives me a safety factor of 3.8 (for 11mm glass) and the only calculators that specify say this is for a rimless aquarium. No type of bracing is specified.

Calculator here.

From what I can gather, it seems that my aquarium could be rimless and safe. My new idea is to remove the eurobrace at the end with the overflow. I would then add a 1/2" strip as an internal overflow. The strip would be angled off the side and joined to the front and back of the tank. I would provide nearly the same amount of support as the current brace except for the angled surface.

 

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Discussion Starter · #19 ·
How would the water get out of that trough? A bulkhead fitting would do it.
Exactly. I wasn't even going to bother with a bulkhead, just leave a few holes out the side. The water would flow out into an external box. In order to go straight to plumbing I would need a much larger box on the inside. I want to keep it as small as possible, so it will probably only come out from the side wall about 1" and the hypotenuse will probably be around 7" so that I will have enough room to drill holes out the side. The external box would be bigger so I could plumb out the bottom and support the plumbing with the stand.

What I'm not sure about is messing with the bracing. I think the weir will be a sufficient substitute for the brace I will remove, but I want to be sure. The reason I want to remove the brace is so I can have access to the inside overflow box for cleaning, etc. and with the brace in place I'll have a very small opening to reach inside the box. The bracing would come out about 3" beyond the overflow.
 
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