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Tank seal decay

oddn0ise

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Joined
19 Nov 2011
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202
Location
South West London
My tank is heading towards its 20th year and am starting to get nervous about the seals going. One area on the front face has decayed, there's algae on it and the sealant has worn thin, its just in a small area 4 cm in length and the decay is to about half of the depth of the sealant.

Anyone have any good ideas for the best way to clean it up and repair it...

thanks
 

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tam

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5 May 2011
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1,118
I would opt for new, it's going to be a pain to do either way and with a tank that age you could fix it up and then have a problem with another area shortly afterwards. New tank, you could have an opti-white front glass (I bet there are a few scratches on your glass at that age too) and the silicone is done a lot neater now.
 

mort

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15 Nov 2015
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1,746
I find that if it worries me, I'll not stop thinking about it until I have done something about it. For peace of mind with a tank seal you would either need to break the tank down and reseal it all (new silicon doesn't stick to old silicon very well). I've done bodge jobs in the past on these kind of areas and they have worked but still had that thought in the back of my mind.
 

oddn0ise

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19 Nov 2011
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South West London
I would opt for new, it's going to be a pain to do either way and with a tank that age you could fix it up and then have a problem with another area shortly afterwards. New tank, you could have an opti-white front glass (I bet there are a few scratches on your glass at that age too) and the silicone is done a lot neater now.
Patch for now, as I think it's all OK, next time around it will be a new opti-white tank, opti-white wasn't used that much then, and yes it does have a few 'painful' scratches.
 

oddn0ise

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Thread starter
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19 Nov 2011
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South West London
I find that if it worries me, I'll not stop thinking about it until I have done something about it. For peace of mind with a tank seal you would either need to break the tank down and reseal it all (new silicon doesn't stick to old silicon very well). I've done bodge jobs in the past on these kind of areas and they have worked but still had that thought in the back of my mind.
Was hoping to try silicon on silicon and hope for the best. It's the getting it cleaned up that will be the trickiest part.
Any suggestions?
 

mort

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15 Nov 2015
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It's tricky because the old silicon really affects how well the new silicon will bond. If the old has splits or dirt you get weak points and it's extremely hard to make sure it's bone dry if there has been water ingress under the old. You can use meths or rubbing alcohol to clean the area but I don't think you'd ever get it clean enough to have a really strong bond.
For me when I've bodged these (and it's when I know there is only a tiny leak or that most of the seal is still ok) I've added a corner strip on the outside so it looks like one of those old framed tanks. It's easier because you can cover the whole of the silicon bead with a wide safety margin on the glass (as the bead is wedged between the glass butt joint). It's not as strong perhaps but it relies on the original silicon being mostly intact. It's looks messy unless you frame the whole tank but it's always been a stop gap until I've built a new tank.
 

tiger15

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14 Mar 2018
Messages
672
Location
USA
My tank is heading towards its 20th year and am starting to get nervous about the seals going. One area on the front face has decayed, there's algae on it and the sealant has worn thin, its just in a small area 4 cm in length and the decay is to about half of the depth of the sealant.

Anyone have any good ideas for the best way to clean it up and repair it...

thanks
20 years sound about time to treat yourself to a new tank!
I’m not sure if silicone sealant has expirating date. I have one 75 gal going on for 35 years, and another 30 years, still holding water tight. If a tank sealant fails, it tends to occur younger. I had a 30 gal newer tank leaked in 4 years, and my friend had a 90 gal new tank leaked in 2 year.. I have no idea why one tank lasts forever, another tank has a short life.

It appears the break is only superficial, and if there is no seep emerging, I wouldnt do anything other than to watch closely. Resealing a leaky tank requires stripping off all old sealant and replacing with all new sealant. Resealing partially will not work as new and old sealant junctions do not form strong bond. This requires emptying the tank to dry out for at least 2 weeks and test filling to assure the new seal holds water. There is lot of work and for big tank located in a vulnerable area, I won’t take the chance and just buy a new tank for replacement.
 

oddn0ise

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19 Nov 2011
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202
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South West London
Have gone for the bodge just help out the sealant that is thinning a little, but in 2 more years it will definitely be time for a new tank.

Have made a first time trip to Aquariums Gardens and was blown away, excellent set-up and service and am now about to do my final scape, and so far, taking it patiently.
 
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