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I have just taken deliver of a used 600 gal aquarium although by the measuements I get about 550 gals. Inside numbers are 34.5 X 34.5 X 95 all in inches. I am going to reseal it as it is about 6 years old and started out as a saltwater tank but was most recently fresh.What I have detirmined appears to be using a razor blade cut out all silicone at corners of tank,clean with acetone or alcohol let dry and apply new bead of silicone pressed in with finger.Makes sence to me accept the acetone or alcohol.My concern is with residue or clean up of it.Any input welcome or other ideas on this also. Thanks

The alcohol may contain "stuff" that will leave a residue, particularly if it's alcohol that has been treated to not taste nice (like industrial stuff, sold without paying taxes to the relevant wine/spirits authority, rather than the Vodka or Whiskey in the liquor store). This can be solved a few ways:
1. You find some MEDICAL ethanol.
2. You rub it with Vodka, which is almost pure alcohol anyways ["Absolut" vodka is distilled to 96%, which is as pure as you CAN distill ethanol in presence of water].
3. Use cleaning Isopropanol (sold for medical and industrial/electronics cleaning purposes).

If you use "industrial" acetone, it should be perfectly fine as a degreaser, with no noticable residue. If you buy acetone for nail varnish removal from Walmart, HEB or some such, you'll probably find that it contains all sort of different additivies, including oil (reduces drying out of fingers), colours (to make it look nice), fragrance (make it smell better than pure acetone), etc, etc. Don't use that for this sort of work. If you want to remove nail-varnish from your nails, go ahead and use that, but for fish-tanks, use the "industrial" neat acetone.

Note that acetone is highly volatile and will evaporate in an instant. If you see some "rainbow" (oilspill on water) effect after you've wiped piece, it's most likely because you've got some grease that got partly solved with acetone and left a gradual residue around the clean area which will cause a rainbow effect.

If you're still worried, wash any area that you've cleaned [after it's been sealed] with a dose of vodka. When finished, you may use the rest of it for drinking if you like...

Finally, I'm sure you'll want to TEST the tank before you load it up with decorations and stuff, so you'll flush out anything water soluble with the water you fill the tank for testing purposes, right?

Best of luck.

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Mats

I've resealed (6) smaller tanks. Four 10 gallon tanks, (1) 15 gallon and (1) 29 gallon. Three of these tanks needed resealing because of leaks. It was my novice errors in tank placement that led to the leaks. They either weren't on a level surface or I tried to move them with some wet substrate in tank. My bad! Since then, I've noticed most 10 gallon tanks I purchase come with gaps in the silicone sealant, so I just reseal them before I use them.

What I've noticed is that the sealants that are readily available, even in the "caulking gun" size, are meant for smaller tanks. The directions usually state "for smaller tanks," but never give a size. So, I called the manufacturer. The initial answer I got was "less than 55 gallons" for the readily available aquarium sealants. Anything above that, and something stronger is required. I didn't think to ask what that was at the time. Sorry. I would imagine a 500 gallon tank would require a fairly strong sealant. If you haven't already, I would call a tank manufacturer and ask them what kind of sealant to use and where you can find it. From what I gather, once the glass gets thicker, a different silicone strength is required. If someone out there knows, can you please verify this?

As for solvents, I've had no problems with rubbing alcohol. The only thing I find I need to do is keep a window open from the fumes. Whichever solvent you chose, you'll need a lot of it. If you wash the tank out with tap water or waste water from the RO filter, this allows you to test for leaks and rinse out the solvent at the same time. I usually let the water sit in the tank overnight. In your case, you may want to do this project in "sections" rather than the whole thing at once. I don't know if that's possible. Are you going to be able to turn the tank over to access the bottom?

Mats: 2. You rub it with Vodka, which is almost pure alcohol anyways ["Absolut" vodka is distilled to 96%, which is as pure as you CAN distill ethanol in presence of water].

Viktor: a likely small correction: 96% is close to 50 volume %; 100 volume % would be 200% or 200 proof, so absolut vodka is about half ethanol half water. The last statement in brackets appears true to me as water and ethanol do form an azeotropic mixture that cannot be separated by distillatiuon/evaporation any further.

No, no, no. 100% is 200 proof, yes. 100 proof is 50% volume alcohol (and the test for this is that it ignites when mixed with gunpowder, or some such_. You obviously CAN NOT produce 200 volume % alcohol - that means 2 x the total volume - it will spill over!. It is still 96% volume (or weight, I'm not sure which) and 4% water. And yes, that's 192 proof. And I think in the US you can get some high-proof spirits.

A lot of people seem to say things like "100% proof", which is technically incorrect. That would be 50% or 100 proof - one uses percent and is exactly half of the other that DOESN'T USE percent.

It gets even more complicated in the old terms in the UK, but here's the WIkipedia history:
http://en.wikipedia.org/wiki/Alcoholic_proof

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Mats

Yes, Mats, you are correct. After I had written my prior comment, I thought about it and realized that I just did not think vodka could be almost pure ethanol. Vodka in my apparently skewed belarussian mind has always been associated with 40% by volume. So when you wrote that absolute vodka is 96% by vol, I for some reason decided that this is impossible and that you meant 96 proof. Anyway, yes, you are right, sorry. And yes, the remaining 4 vol % of water CANNOT be removed from ethanol-water mix by distillation.

No, you certainly wouldn't want to drink 96% ethanol without diluting it. Which is why the plant where they make Absolut vodka, they then put back enough water to make it 40-50% strength for drinking purposes [and I don't particularly like neat vodka anyways - mix it with something, sure, no problem].

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Mats

I've resealed two tanks in the last few weeks, a 55 gal long (made in 1983) and a 27 gal hex (1987). They have been holding up so far well. 27 gal also features a crack across the entire one of the 6 facets and a small portion of the corner was crushed (20 years ago).

My steps were:

(1) using a razor/scalpel cut out old silicone (Si); scratch any Si residue off the walls (do not put fresh silicone over patches of old silicone, no matter how small)
(2) sandpaper the areas where new Si will be placed along the seams - the small scratches and grooves make for a far, far better adhesion (I find even with clean and degreased but smooth surfaces, the Si does not adhere well, e.g., to plastics)
(3) wash the tank with dish detergent and pot scrubber and rinse very thoroughly
(4) air dry thoroughly
(5) degrease well with denatured alcohol (soaked paper towel); allow to evaporate (will occur quickly, minutes, at 65-75 F)
(6) place a generous bid of Marineland aquarium Si (half of the standard caulk-gun-size tube was enough to seal both tanks of mine) and semi-firmly smooth and press into the corners/seams with a finger (wear a thin nitrile glove, e.g., used for a medical examination)
(7) follow the label; 2-3 days at around 60 F and the tank is ready for a test, when you do not smell much of acetic acid anymore (vinegar odor) - as long as the smell is there, that means the sealanlt is still curing

I am sure someone will find that I did not do something right but that's how I did it.

Viktor

By no means do I want to spoil all the alcohol/aceton/silicon fun. But there's one thing you should consider before starting with the razor action. If you have an insurance that will cover damage caused by water from your tank, you might want to check whether they'll still pay when the tank in question has been tampered with by a non-professional. 600gal is a lot of water and can cause serious damage.

I must confess that I am too much of a chicken to try and reseal such a large tank myself. But apart from that what Viktor says sounds good to me.

And no, you really don't want to drink pure alcohol. I once tried 80% rum - not a very smart idea.

Acetone is by far the best solvent to use to remove traces of old silicone after you have removed all the old sealant you can through mechanical means(razor blade).

I have never tried to repair any tank larger than 175 gallons but while testing the the repaired tank for the first time it's front pane broke. The tank was at the head of the stairs to the basement of my old fish shop which I happened to be walking up at the moment of failure. The deluge washed me all the way back down to the basement floor. I was really lucky none of the glass cut me me but at the bottom of the stairs in the basement is where my mother kept her pet Stumptailed Macaque, a 45 lb small version of a Baboon. It was one mad monkey and it was trying to stay off the floor by hanging on to the pole it was chained to. He finally gave up and jumped on my back chattering his displeasure very loudly. He not only disliked being flooded out but he did not like me so he was resentful that I was his only island in the flood.

I salvaged enough of the glass from the failed tank to build a 48 X 24 X 36 inch tall aquarium of about 90 gallons. Unlike the tank that failed, I built it's successor as an all glass and silicone tank which lasted for years then was eventually sold.

Building a 600 gallon tank is beyond any tank I have ever built.
I don't suppose there are any physical/material reasons why an all glass aquarium could not be built provided the glass is thick enough and the bonded surfaces are sufficient to develop the full strength of silicone sealant.
I would probably look into a composite design which used wood framing and epoxy protection for the wood. I would go with all wood sides with a front glass viewing panel. 600 gallons is a large tank by any ones' standards.
I think I would opt for a licensed, bonded contractor experienced in large aquarium construction. Username, "Whitepine" used to post and he has built some tanks of around 2000 gallons successfully for some restaurants or bars.
If I had the room and money I would love to have such a tank for a large group of wild Discus set up biotope style. Fear not, I would also have plenty of catfish stocked in it too.
The various monsterfish sites have some examples of concrete constructed tanks in excess of 10,000 gallons described. Some people have made such tanks and they rival public aquarium systems. But for Pacus and Arowanas? Don't think I would be willing to go to such expense for typical monster fishes.

the Macaque story is precious, Larry!!! I can just picture a resentful angry monkey forced on the back of a man it hates

Mine was the only dissenting vote against acquiring monkey out of five mine was the only nay vote of 5 about whether we should buy the stumptail macaque. My vote was disregarded but monkeys should not be kept as pets.
Every thing I cited as reasons against keeping one as a pet proved to be the correct assessment. I knew that eventually it would be myself and my brother who would be assigned to it's routine care.

apistomaster wrote: at the bottom of the stairs in the basement is where my mother kept her pet Stumptailed Macaque, a 45 lb small version of a Baboon. It was one mad monkey and it was trying to stay off the floor by hanging on to the pole it was chained to.

I do hope the poor monkey is not longer there. Keeping a monkey by itself chained to a pole is just horrible. But I'd say you were lucky that it protested only verbally, it might as well have put those teeth to good use. Having 175 gal come at you must have looked very "interesting", though. How long did it take to dry out the basement?

I agreed with the idea monkeys should not be kept as pets but the family vote was 4 to 1.

The basement had a sump pump and drain which made the clean up easier