Hi
You really want to start an argument ,don't you?? lol
I personally have used many different kinds and have never had a specific toxic issue. If you only want a small amount
get the type made for aquariums. They are more expensive but not much for small amounts.
I find GE silicone type II to be very good . Some supposedly have various additives that may or may not be toxic. For a small amount why risk it?? gary

If it labeled 100% silicone, that's what it is, and it's the identical product, regardless if labeled for aquarium use and priced at 10 times more, or sold in hardware shops and home centers for sealing tubs, showers and refrigerators.

I buy it in the larger tubes meant to be used with caulking guns and have used it for years to reseal tanks with no problems. To give me more control on small jobs, I filled a 30 cc syringe that came with a fairy narrow tip on it and keep it capped, inside a zip bag. It's handy for just the type of small job you are planning.

That syringe originally held paste horse wormer, but after being washed and boiled, I was sure it would be safe, and it has been.

I don't know if it's available in the UK, but in the US, 100% silicone is also sold in small syringe applicators, for small jobs. You might want to see if you can find it there, because they are a lot easier to use and control, than squeezing it out of a tube.

To keep any remaining sealant in the tube fresh for another use, dip the tip into hot water immediately after use, wipe it clean, cap it, and seal it into a zip bag with the air squeezed out. My refill in the syringe has so far kept good for nearly 4 years. I used it only last week, to seal a small crack in a plastic box filter and it flowed and held as well as the day I had opened the original large tube.

Woaaaaaah! No I'm definately not the kind to start any kind of argument, on-line or otherwise...I couldn't even win a bet, I am too quiet, and at 6ft I TRY and blend into the background...believe me that's not an easy job!!!!
Haha! (: ¬ p)
Thanks for the replies both of you. Was just curious as we have tubes of the DIY stuff in the garage, to get the real McCoy would enlist a round trip of 20 miles or so as we're out in the sticks.....so I thought, why do that if I don't need too especially as fuel has now topped £1:05/litre here!
Gary...realise you were only "pulling one of my (lonnnnng) legs!!"
Regards, Gill.

Gill
I've been on forums where this question really induced an argument !!lol Some of the silicones have added algae and mildew retardents,says so right on the label, . I read an actual statement from
Dow Corning the manufacturer of them and they said that it could be toxic to certain life forms , They took no responsibility as to the safety of the product.
In my own experience I've had no problem.. The conclusion of the last debate I read was why run the risk?? Makes sense I guess if you're only using a small amount.
In your case I'd go ahead and use what you have. Something to watch for as time passes.
I've also used fiberglass tarps in my ponds rather than liners with no ill effects but many people will argue the point lol. One has been in place for 25 years .Still does not leak and two fish survived 20 years . Can't be too toxic lol gary

Yes, I can definately see where you are coming from, it's far better to be safe than sorry, so I must admit I agree. I DO realise you meant it in a friendly way and you are only trying to advise...which after all is what I was seeking in the first place!! Been into the depths of hubby's garage and read the labels, ours are by Dow Corning also and contain mildew retardant etc....so....to the fishy place we will go as I like my fish too much!
Cheers 'n all that!
Gill.

Gill
Didn't mean to scare you off. lol I figured if I recommened it others would jump in with dire warnings lol
Have no idea what they're using as a mildew retardant but in my experience both algae and mildew will grow on it lol. One question that I asked but did not get an answer .
The label says that it is 100 percent silicone so how can there be added ingredients?? I thought 100 percent means that's all there is??? Of course if a product is not intended for consumption they are not required to list the contents and they don't lol.
I myself would not hesitate to use it.
Birdwidow has obviously had no negative effects either.
Oh well, good luck with your project no matter what you decide. gary

We use a lot of silicone in the aerospace industry and we have very stringent standards about resistance to mildew and other things. Silicone by itself has nothing for mildew to feed on (it has no hydrocarbons) and the reason you see mildew on it around the home is because it gets coated with other things, like soap scum or dead skin cells in the shower -- those things DO feed mildew when the humidity is high. One caution about silicone, though. There are acid-base and neutral-base versions, and the acid-base ones stink like vinegar. Some of the various brands seem to stink for a long, LONG time as they cure. I had one of the "Gunk" products that smelled bad for literally weeks, and now I avoid those completely.

Hope this helps. Normally I just lurk here but today I'm home sick with the flu -- nothing to do, so I thought I'd stick my oar in the water...

- Steve in St Louis

Hi
Found that very useful. I had a tube that never cured one time. Stayed almost sticky and had no stregth at all.
Do you think any of the types are toxic once cured??
IME the stuff to prevent mildew and algae works about 30 minutes. lol Whatever it is doesn't last if at all. gary

100% silicon does not mean its pure per se. There are different types of silicon. If it was 100% pure then it could not be a gel, it would be a solid, so with that, silicon is a glue based off the element silicon.

Its like when you say you put nitroge into your tank. Your not putting nirogen, your putting a chemical that contanins nitrogen and there are hundreds of them, potasium nitrate, sodium nitrate and the list goes on.

So with that, I would steer towards the more expensive kind that is made for aquariums. However if your just using a dab, I would use any kind you have on hand.

That's very interesting, but I've been using GE clear exterior "100%" silicone caulk to reseal tanks for years, with no ill affects on the fish or plants, along with just about everyone else I know who does the same.