Hello; I agree that being out of level is less of a stress than being "cocked" or "catty-cornered". By that I mean the diagonal corners not being true is more stress that one end being slightly higher than the other or in the same sense the front being higher than the back.
When is a tank too old?
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What you said is accurate, and I agree with you 100%. To complete a lasting resealing job, you need to do it to the perfection: glass absolutely clean with no foreign molecules. Hand steady and fast to dispense silicone in one continuous bead. In actual practice, many resealing failed to last due to imperfection or taking short cut by first timers.IMHO there is a big difference between re-building and re-sealing a tank. Either procedure is a PITA. Simple in theory, but tedious, time-consuming and wearisome in practice. Done correctly, the result is completely trustworthy and permanent. Done incorrectly...it isn't. And here's the catch: every inch of the total linear length of all the seams must be equally perfect. One bad spot, one imperfectly cleaned area, and the whole thing is a waste of time.
If it's an actual rebuild...where the glass panels are separated and then re-assembled...the same holds true, but it is literally two or three times as much work.
It's not a secret; it's very simple. Every square inch of glass that is contact with silicone must be absolutely clean, dry, oil-free and pristine. There must be no trace of old silicone left in place, and that's where most re-sealing jobs fall flat. New silicone will not adhere to old, cured silicone, so the old stuff must all be removed. Miserable, tedious work. "Good enough"...is not good enough.
A fellow for whom I worked building tanks almost a half-century ago was a little OCD, and so he was well-suited for this sort of obsessive attention to detail. He was such an artist with silicone that he would lay out the pieces of spotless, pre-cleaned glass on the tabletop, complete with jigs he built himself, in a room that was kept as clean and sterile as an operating theater. He would lay out a bead of silicone so precisely that when the glass was assembled, the amount that squeezed out of the seam was perfect for a quick finger wipe to create the internal sealing bead.
We mere mortals usually lay out a small bead that becomes the structural joint between pieces of glass, and then immediately after that apply a small bead around the entire internal seam length that is immediately smoothed into the sealing bead. This all has to be done fast, before any of the silicone begins to skin over.
Keep in mind that the structural bead is usually sufficient all by itself to create a strong, permanent water tight seal. The extra sealing bead is just a safety feature, in case there might be some tiny blip in the structural bead which doesn't put the assembly at risk of coming apart, but which might allow a slow leak.
So, if you have an older tank that has developed a slow leak, it's rarely necessary to re-build it. Strip off all the old internal seam...every last molecule of it...but leave the structural bead strictly alone. Replacing the internal bead will solve all your problems.
Oh, and the "old tank" thing? There must be a limit, but it's way, way higher than most seem to think. I know of at least three all-glass tanks...one of which I built myself, and the other two while assisting The Guru, that are over 50 years old and still holding water beautifully. Part of the reason is that back then, tanks were not made out of the thinnest glass imaginable; we used thicker stuff, which vastly increases the surface area and therefore the strength of the structural bead. 6-foot tanks were built with no cross-braces, and functioned perfectly. But the main ingredient is simply relentless, obsessive, unwavering attention to detail, mostly in cleaning.
By the way, those older thick-glass tanks were also better suited with their thicker structural seams to very slight imperfections in the stand. When you have a tank that suddenly, inexplicably begins to leak, the reason is often a stand that is not completely flat. Leaning a wee bit one way or the other is not the kiss of death many think it is, but if the tank is not completely and evenly supported all the way around...if it, for example, teeters a bit corner to corner...the stresses this sets up can be a tank-destroyer. Thinner glass tanks are more susceptible to this, and the cheaper-is-faster-is-better mentality that creates those tanks also contributes to stands that can just barely support the weight of the complete set-up, and which may very well be imperfect on the top edge.
Again...they don't build 'em the way they used to...
Regarding age of tanks, I am glad to hear that 50+ year old tanks still hold water. I have one 40+ year old and three 20 to 30 year old big tanks in continuous use with no leak. I worry less about tank leak in my basement, but there is not one day I don't worry about leak of my 125g and 75g in my living room. To prevent flooding disaster, I never leave out of sight during my weekly water change, and installed ground fault outlets to safeguard against equipment leak and subsequent short, but nothing can I do about spontaneous tank leak due to old age. Most spontaneous leaks I know of are newer tanks due to manufacturing defects. Hopefully, my tanks are well built enough to be ageless.
Whereas well built tank can be ageless due to integrity of structural seam, I am wondering whether interior seam has age limit. I notice structural seam in my tanks stay clear, whereas interior seams blacken over time what appear to be aquatic erosion. Some fish such as Royal pleco are known to graze on silicone, so can micros and algae penetrate exposed silicone. If so, a reseal tank may eventually leak due to erosion of interior seams.
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I have had many floods over the years, as a result of forgetfulness (leaving water running and becoming distracted or called away), carelessness (filling hose not being watched, flopped out of tank and onto the floor), poor tank construction (brand new commercially-built tank split a seam from top to bottom only a few weeks after initial filling) and other problems I am trying to forget. Since that last one, I have never purchased an all-glass tank bigger than 75-gallons, instead building my larger ones with plywood because I simply trust it more. But even with that proviso, I have only a couple small tanks on the main floor of my home; everything else is in my unfinished basement to alleviate my worry about leaks, floods and catastrophic failures.
I long ago stopped wondering about the darkening that is so often seen in the sealing bead in all-glass tanks. Yes, the structural bead always remains unchanged, while the sealing bead goes black or green, begins to suffer feathering of the edges, etc. This happens even in tanks with no plecos or snails or other sucky/raspy feeders. I've also seen tanks where ham-fisted OCD owners were so overzealous in their razor-blade wielding that they badly damaged the sealing bead. But, again, in a properly-constructed tank, the sealing bead is really just a feel-good just-in-case kind of addition. The structural bead, if applied carefully, quickly and properly during initial construction, is continuous and water-tight. It would be an unusual case indeed for that bead to allow a leak, assuming that you don't cut into it while cleaning the glass.
Honestly, I think the main reason why every all-glass tank has the sealing bead is the simple fact that it is easier to build a tank with one rather than without one. When the glass panels are assembled into a box, there is an inevitable small amount of silicone that is squeezed out of the seam, both inside and outside. The outside one is easily sliced off after it cures; the inside one is more problematic. If you try wiping it off immediately, you just create a smudged sloppy mess and also are applying pressure that tends to "wonkify" your nice square joints. If you wait for it to cure, it can be carefully scraped off, but that is far more work than simply running a finger (human or robotic) along the seam immediately after assembly. That requires only a very few seconds per tank and thus reduces costs. And of course, a smart marketing fellow sells it as an extra measure of safety and reliability...because calling it a cheapskate move to save a few bucks per tank doesn't sound good.
This whole issue can be largely solved by masking tape applied all along the length of each joint before assembly, but that's still more work and more cost, and it is still not nearly as fast or foolproof as the old licked-finger trick.
Hint: always lick a fresh, new finger for each swipe of your bead-smoothing procedure.
I'm not at all certain what you mean by "aquatic erosion". This whole topic is one regarding which I would love to hear a few more viewpoints.
wednesday13
,
Backfromthedead
,
thebiggerthebetter
are all experienced large-tank builders; how about it, guys?
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What I meant by aquatic erosion is degradation of silicone in aquatic environment from physical, chemical and biological elements. Physical and chemical damage of silicone by owner, fish, and inver can be prevented, but not micros. If the interior seam blackened over time, it’s an indication that moisture has penetrated through the silicone allowing micros to thrive. My question is whether such inevitable blackening over time can degrade silicone to the extent of separation from the glass causing leak. A well built tank can last over 50 years as reported, what is the record of a well resealed tank can last.
Had a feeling you would continue to tilt at this windmill. Having done some sealing jobs I can testify that while it needs to be done properly it is nowhere near needing to be perfect at a molecular level. To reseal a tank the inside seams need to be clean and dry. If it is a newer tank which came with silicone on the inside seams, I cut the old away and work at cleaning residual bits of silicone. Such can take some time and may have you trying some different approaches.
Once the old silicone is removed a common thing for me was to clean the inside of the glass. Clean off algae, lime scale nd any other buildup. That involved rinsing with water. Even if such cleaning is done before cutting out the old silicone a fact remains the reason was a leak. That means some place along the seams there was a leak, so water is in the seams. A last step before applying new silicone, for me, was to get the tank dry. On smaller tanks I would set them in the sun. On bigger tanks I would rig up a lamp to shine inside the tank and let the heat dry out the seams, sometimes for a day or few.
I suspect you are making up the term "aquatic erosion". Such does not seem to happen.
So, what i must assume is a silicone sealed tank is reported to have lasted some 50 years. I fell in love with silicone as an aquarium product soon after I first discovered it existed. Maybe in the 1970's??? I found ways to use it other than sealing tanks. I built interior structures of glass bonded with silicone. I salvaged pieces of a slate chalkboard removed from an old schoolhouse. I used the slate to make decor and other such for tanks, again at least as early as the 1970's. I do not know when aquarium grade silicone became first available, does anyone?? My point being there could be some old tank from the dawn of silacone still in working order. May be that a silicone sealed tank situated in a stable environment may hold tight for decades to come.
Many decades ago I happened by a department store and saw glass shelving being discarded. It was scuffed up some but much was not broken. I collected a bunch of it. I used it for tank covers and such. I bonded two such pieces together to make a longer piece. Bonded them on the flat surfaces with about a six inch overlap. That again was in the 1970's. That piece is still well stuck to this day. I have tried to separate them to no avail by pulling on them. I hesitate to try to pry them apart, after all it is glass. Point being the old silicone holds up.
