Staplez Posted January 18, 2005 Report Share Posted January 18, 2005 I have a tank thats getting a bit old at the joins. Its over 7 years old and some of the silicon has come away when cleaning the glass. It would spell disaster if I was to put the 150 littres of watter in there. Its a tall hex tank. How is the best way to go about re-appling silicon to the glass. Im expecting to strip it all off. But should I strip off a load of it then replace it and keep doing so untill I have replaced it all. That would help hold it in its hex shape or does that not sound like a good idea? Quote Link to comment Share on other sites More sharing options...
morf Posted January 22, 2005 Report Share Posted January 22, 2005 last time I re-sealed a tank i chickened out and cut as much sealant away as I could but left a tiny strip to hold the glass in place. then I applied my silicon sealant and all went well. I guess if you did it stage by stage it would work fine - so long as when you pull a strip of old sealant off it didnt tug up the corner of your new sealant and leave a hole for water to work away at. it is surprisingly good stuff silicon sealant, when you think about the pressures it withstands. Quote Link to comment Share on other sites More sharing options...
Dark Posted February 18, 2005 Report Share Posted February 18, 2005 i was talking to our local wellington tank-maker about re-sealing tanks and found his point of view rather interesting... Typically when i find a tank has a leak i pull the whole thing apart, clean off all the silicon and start again. he approaches it in a slightly different manner: The silicon between the sheets of glass is for structural support, the silicon on the inside of the tank is for keeping the water in the right place. when rebuilding a rather large tank i got him to make up the top supports for it, and he decided that the seals on the inside needed re-doing. he cut them out and put them back in, without so much as asking what type of silicon i used (tangental information regarding some silicon sealants not sticking to others). i think the moral of the story is; if the tank is not trying to fall apart when you cut away the water seals on the inside you probably don't need to worry about them, and it would seem that silicon is strong enough to support this theory Quote Link to comment Share on other sites More sharing options...
suphew Posted February 18, 2005 Report Share Posted February 18, 2005 Assume you know there are two types silicon (cure two different ways), one of which doesn't work. I can never remember which is which but I'm sure one will tell us, the one you want is the really strong smelling one and seems to me to be less common in shops. Quote Link to comment Share on other sites More sharing options...
Dark Posted February 18, 2005 Report Share Posted February 18, 2005 Assume you know there are two types silicon (cure two different ways), one of which doesn't work. I can never remember which is which but I'm sure one will tell us, the one you want is the really strong smelling one and seems to me to be less common in shops. i went into placemakers and asked one of the sales assistants - he got on the phone and rang to speak to the chemist that makes the stuff! interesting... most of them say on the back of the container 'not for aquarium use'. this is generally because they contain a mould inhibitor which is toxic to fishtanks. if you get to a fairly decent hardware store you will find a huge range to look through; there are some that state they can be used. There was also some talk (somewhere) about the different curing types - one that uses chemicals (like alcohol) when curing and one that uses a 'neutral' cure (i don't personally know the specifics - air?) - what i have found is simply that it doesn't matter unless you are not planning on waiting for the silicon to cure totally before using the tank (something like 24 hours per cm thickness from surface of silicon in contact with air; two 10cm square pieces glued face to face would therefore take 5 days to cure right to the center) - once it is cured you won't have any problems unless there is a mould killing thingee in the equation. you can get stuff from some pet stores that does the trick, but (as with most tank lights) its the same stuff in a different package at 10 times the price - go to the hardware store!! Quote Link to comment Share on other sites More sharing options...
Lucid Posted February 18, 2005 Report Share Posted February 18, 2005 Which placemakers did you got to dark? We sell 3 types at kaiwhara and they are the Fosroc Silaflex RTV which is quite smelly, Holdfast 202 clear, which doesn't smell very much at all and selleys glass sealant is the 3rd, which I haven't used as of yet( but have a tube here ready to go). You will probably find they are an acid based( for etching the glass to give the silicone something to stick to) and what they call nuetral cure, which means there are no solvents in it to leech out into your tank. B Quote Link to comment Share on other sites More sharing options...
Dark Posted February 18, 2005 Report Share Posted February 18, 2005 so thats what they were getting at with the curing thing... placemakers... kilbirnie the stuff i use comes in a mostly white tube with some black and blue, and a bit of red.. i think. i'll check it out when i get home and let you know. one thing i can recommend not using would be sellys space invader. i guess acid etching would not be such a bad thing on the external seals - it is usually recommended not to use machined glass on the edges of the tanks because the silicon has less to stick to (more random information from other local glaziers) Quote Link to comment Share on other sites More sharing options...
suphew Posted February 18, 2005 Report Share Posted February 18, 2005 No you MUST use the correct one, I have been there and done that, the incorrect one DOES NOT WORK, it might not fail straight away (it did for me 3 x in a row, luckerly when I was testing to make sure it worked. As soon as I used the correct one, no problems) but it will fail. It is the really smelly one you must use, plus it doesn't harm your tank, can even be used underwater, I just glued a tap into my new marine setup a month ago, waiting maybe 1/2 hour or less before filling with water, if I can do this with marine inverts in the tank there is noway it will harm fresh water fish. You have been warned!! :lol: Quote Link to comment Share on other sites More sharing options...
Dark Posted February 18, 2005 Report Share Posted February 18, 2005 yeah, i was referring to using a toxic one for gluing the glass together and a non-toxic one for creating the internal seals to keep the water in place - not that i can see any reason to go out of ones way to use two separate types of sealers! i guess the only question left is; what glue has who used for what purpose; what works and what doesn't? Quote Link to comment Share on other sites More sharing options...
Jo1 Posted February 18, 2005 Report Share Posted February 18, 2005 I totally agree with Dark. Take it to a glazier and get it redone, Those hex glass tanks can develop leaks easily and it would be far safer to get it done by a professional. Quote Link to comment Share on other sites More sharing options...
Lucid Posted February 18, 2005 Report Share Posted February 18, 2005 Like I said in my earlier post, I have used the fosroc and the holdfast, one is smelly one is not, and they are both fine, the advantage in usuing the holdfast 202 clear, is it dries much clearer and doesn't go opaque with age. JMO, but any of the 3 above would be fine, plus what you have to remember that for the companies to put "Aquarium Safe" on the product it needs to so, and extensively tested, and if you find it not to be so then you are eligible for compo under the fair trading act as the product is not " Fit For Purpose" B Quote Link to comment Share on other sites More sharing options...
Pegasus Posted February 18, 2005 Report Share Posted February 18, 2005 The Siiaflex RTV Glass And Ceramic Professional Range Silicone Sealer is the one to use. It is safe for the fish... recomended for aquarium use,... and can even be used to seal leaks in a full tank that is leaking. I've built dozens of tanks using this stuff, and would use no other. Warren's big tank was sealed using this stuff. Can't remember the litres, but it was eight foot by two by two I think. Around 13bucks a cartidge and is available at any decent hardware store. Bill. Quote Link to comment Share on other sites More sharing options...
gunnstack Posted February 19, 2005 Report Share Posted February 19, 2005 There are a couple of things you want to watch out for. Firstly make sure the Silicone you use is is suitable for fish tank use (check the fine print!). Secondly make sure it is still within it's use by date. I have used some aged Silicone and within 6 months it broke down. The Silicone you need is supplied by a number of companies and uses Acetic Acid as the curing agent. It smells like very strong vinegar. You can use it to seal tanks but only if the fish are already removed. The acetic acid will etch the glass giving you a really good bond If you use the product and are asthmatic or have other lung problems leave it to a professional. I have built and re-built tanks but you really do need to use an extractor system a mask or a fan to get rid of the fumes. Remeber you are working in an enclosed environment when working over a tank-the fumes wil rise upwards. Acetic acid is not of itself toxic but the lungs in particular are susceptible to the irritating fumes given off during the curing process. It is also a skin irritant so anyone with a skin problem should take appropriate precautions. If all else fails-read the instructions!! Hope this has been of some help. Regards Gordon Quote Link to comment Share on other sites More sharing options...
Graeme Holden Posted February 21, 2005 Report Share Posted February 21, 2005 most of the acid cure silicones will continue to cure in water, in fact on buildings that I used the stuff on, if you want a really fast cure you can spray a fine spray of water on it and it will go off really fast, but ofcourse you cannot beat a slow cure, silaflex from memory is a really good product as one person mentioned, and fosroc also very good quality, but the chemist of any product will advise you or go on the web and find out that way, years ago I worked part time for Hori Parker in Wellington, some may know him, he made great tanks and always used the acid cure silicone, he would be very old now, anyone know anything about him at all, tks Graeme Quote Link to comment Share on other sites More sharing options...
gunnstack Posted February 22, 2005 Report Share Posted February 22, 2005 I have had a long association with the paint industry and Silicone products were one of the mediums I worked with. "Some" silicone's require a certain amount of moisture to cure properly-the slower the cure the better the bond-but some moisture must be present. As the previous post mentioned spraying water hastens the cure (surface only!!) but does little to create a really permanent bond with the substrate. Silicone cures in a similar way to paint i.e. it forms a surface skin which allows the active ingredient to work slowly on the substrate and form a bond, gradually realeasing volatiles etc. via the " semi-open skin" . However if the product is allowed to skin too quickly then you can create a sitution where gas/moisture will be trapped within the skin causing air or moisture bubbles to form. Try rolling paint on a wall on a really warm day and you will see what I mean-you will have a mass of bubbles which require to be individually "pricked" - prick of a job and you will probably have to re-do it to make it look reasonable!! Regards Gordon Quote Link to comment Share on other sites More sharing options...
Dark Posted February 22, 2005 Report Share Posted February 22, 2005 The stuff i use is 'FOSROC Silaflex RTV Clear' Available from placemakers for about $7 a tube on a good week, i've used it for everything and nothing has broken. It sells itself as aquarium friendly and the instructions state only that you must use the non-coloured or 'clear' version (clearly marked on the front) as other colours contain mould inhibitors. and it is NZ made in petone Quote Link to comment Share on other sites More sharing options...
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