125 gal resealing/tank construction/expansion questions

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Feb 12, 2007
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I picked up a used glass 125 gal long today as a new home for my 2 Oscars. Ended up with tank, wrought iron stand, visi-therm 250 watt, emperor 400, aquaclear powerhead with 2 new replacement filters, and some other misc stuff for $130.

The tank is at least 15 years old and the previous owner had resealed it a few years ago but emptied it and let it sit shortly after. While the silicone is still blue and pliable the job, on closer inspection, looks pretty crappy and I've decided to redo it. A few questions, though.

1) I was considering completely disasembeling this tank and starting over. I started researching what bonds the actual joints and was completely amazed to find that the only thing holding a glass tank together is silicone. Since silicone has such a high adhesion value to glass I'd assume this means that simply releasing the corners with fresh beads of silicone signifiantly strenghtens the integrity of the tank. Is this correct or am I missing something?

2) Before I stumbled onto that fact I was researching tank construction and found two conflicting methods. 1) The bottom should be inside all 4 walls and slightly higher than all 4 walls so it is never used for support at all. 2) The bottom should be the actual base and all 4 walls should be joined on top of it. The construction of my tank is the bottom is inside all 4 walls but flush with them. The glass is 1/2 but the lip of the stand is 1" or so. Also there are two cross braces running front to back on the stand. Is the design of my tank and stand fine or is this something I need to remedy?

3) The tank currently has no trim on the bottom. I don't really like the look of trim and was simply going to add a 1/2 layer of hard foam or something similar to balance out any imperfections in the stand. Is this sufficient? If so, what material would work best?

4) I also just found out about expansion and consequently the tank won't quite fit where I'd intended it to go. In short, I'm going to end up moving a small wall a bit. How much room should I allow for expansion on a tank 72" long x 21" tall by 19" deep with 1/2" glass?
 

Rbishop

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#1 Have you filled it up and let it set for a couple of days to see if it leaks? If it does, I'd break it down all the way and reseal completely. If it doesn't and you just don't care for the sight of an ugly job, I'd scrape the interior and just re-bead the joints.

#2 Have had glass tanks both ways and seen arguements for and against both. Never had any issues with either style.

#3 All of my glass tanks have upper and lower trim. And I use foam under all my tanks.

#4 By expansion I guess you mean the bowing from the weight of the water? I'd make the area larger in all directions and then trim it back in. Leave plenty of means for access though to maintain equipment.
 

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Feb 12, 2007
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#1 Have you filled it up and let it set for a couple of days to see if it leaks? If it does, I'd break it down all the way and reseal completely. If it doesn't and you just don't care for the sight of an ugly job, I'd scrape the interior and just re-bead the joints.

#2 Have had glass tanks both ways and seen arguements for and against both. Never had any issues with either style.

#3 All of my glass tanks have upper and lower trim. And I use foam under all my tanks.

#4 By expansion I guess you mean the bowing from the weight of the water? I'd make the area larger in all directions and then trim it back in. Leave plenty of means for access though to maintain equipment.
No, I haven't filled it. It's dry now and since I'm planning to reseal either way I didn't want to get it wet.

Regarding the two styles of tanks that's good to know if I do end up breaking it completely down but what about the style of construction it has now considering it's different from the other two I saw suggested?

As far as expansion I simply saw it mentioned in a few threads. How you need to take into account for it when building hoods, tank clearance, etc.. One post I saw said a 125 could expand by as much as an inch over the width of the tank. Just wondering if anyone else had heard of this.

Thanks for the reply. I think you've answered just about every thread I've posted here. I'd have only learned half as much as I have so far if not for your responses :)
 
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