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Floyd R Turbo 08-30-2009 02:18 PM

Re-sealing an 37 gallon
I just bought a 37 gallon off Craigslist for $20 and once I cleaned it out (dead bird and all) I found that it looks to me that the previous owner (who left it in a shop owned by someone else, so no history) apparently got a little too crazy with the algae scrubbing, the silicone on the corners is rather jagged and thin in a couple places, big tears out of it, etc. I haven't filled it up yet to see if it hold water, but I can't imagine it won't. Still, it's bad enough to me that it probably needs re-sealing. This is something I've never done before though, and I read this on another thread...


Originally Posted by Speakerman (Post 992792)
Well, if it were me, I would have bought the tank. It's REALLY easy to reseal a used tank if there are 0 cracks. You basically take a few razor blades, a bottle of alchohol and a clean towell.

Cut the old silicone completely off the aquarium, being sure not to actually stick the blade between the joined glass. Then go back and clean it all with alchohol and dry. Once completely dry, go back and put a 1/4" bead of silicone on each joint/edge, use your finger or a caulking tool to smooth out the silicone, The idea is that a little bit of silicone in the right place is better than a lot done sloppy. If you take your time, you have a 100% chance of sealing up that tank.

...and it sounds relatively easy to do. I'm an engineer and a fix-it guy, so this makes total sense. The last 37 I had (20 years ago) lost a seal and I paid a guy to redo the whole tank and it was thick and sloppy IMO. So I had a few questions before delving into that:

1) Can I run a bead over the existing seal or it is just better to take it all off?
2) What kind/brand of silicone would I buy, where would I get it, and about how much should I need? I'm thinking 1 tube would do it for a 37 at 1/4" bead
3) How drying time before putting water in?
4) Should I take off the top casing? I'm guessing it would be better, but as long as I can get the new seal up to the casing, water won't get over that. Assuming bottom casing can stay where it is since I'm just re-sealing the inside.
5) Do I have to worry about air bubbles in the caulking, like at corners, etc.
6) how tough is aquarium silicone to work with?
7) should I just fill the tank in the garage and wait a month, and if it holds, just leave it? Or is it safer than sorry just to re-seal it, especially if it's not that difficult?

I'm hoping it's not too difficult or expensive, because I like the size of the 37 and I got it so cheap, talked him down from $30

Thanks for any advice!

thominil 08-30-2009 02:26 PM

1. New won't stick to old.
2. Either get it from LFS, or GE has some that is aquarium safe. I thinks it's either GE 1 or 2, don't know right off the top of my head.
3. Letting the new silicone cure for a week is best IMO.
4. Just remove the stuff in the corners all the way up to the brace and reseal it. Leave the brace alone.
5. Yes, you need to worry about bubbles BIG time.
6. It's basically like glue when it comes out of the tube.
7. Just fill it and let it sit for a few days, if it holds, you're all good, if it leaks empty and find the leak.

Silicone is cheap, shouldn't be more than $10 a tube.

Hope this helps.

mfdrookie516 08-30-2009 02:27 PM

1) It would be best IMO to take a razor blade and remove the old silicone first so the new silicone has something better to bond to.

2) You can get "aquarium sealant" at most pet shops, or you can get #1 silicone at most hardware stores. Its all the same, and most will say "aquarium safe" on it.

3) Its best to let it cure at least 24hrs, 48 would be better...

4)That wouldnt be necessary, it would be very hard to do so, and you may end up breaking it trying to get it off.

5)Take your finger or one of those plastic "calk" scrapers to get a nice bead all the way around and you wont worry about air bubbles.

6) Silicone is very easy to work with, but if you get it on anything, you will have to let it dry before you can remove it easily.

7)It would be well worth the $10-15 to reseal it now, instead of having to worry about it leaking later down the road, then having to take the whole thing apart, reseal it, and put it back up... JMO though

Floyd R Turbo 08-30-2009 06:14 PM

Thanks both for the advice. I read up on it a little more and it doesn't sound too hard, and I think it would be worth doing instead of risking a leak or failure down the road.

I have another question though:

After you remove all the old silicone, you should clean the glass but I've read using rubbing alcohol and I've read to use Acetone. Will either of these dissolve the silicone seal that I'm not removing, that is, at the actual joints? Is one better than the other?

Also, if I do end up with any bubbles anywhere, do I pretty much just have to start over? I'm guessing that I'll be able to catch them and work them out, if I work fast enough (<5 minutes for the whole job)

mfdrookie516 08-30-2009 07:24 PM

I always use vinegar to clean my tanks. The last tank i resealed, i just scraped off the silicone, used a sponge and vingegar/water to clean it, let it dry for a couple hours, then siliconed the joints. IMO thats the best way, not sure about using isopropyl alcohol or acetone in an aquarium though, i know it was recommended in another thread not to use a glue on an overflow pipe that had acetone in it, so idk if i would risk it personally

Floyd R Turbo 08-30-2009 08:35 PM

I picked up a couple tubes of the All-Glass brand silicone, and they suggest using isopropyl alcohol. I did read that acetone can dissolve rubber, although it dissipates quickly so it really couldn't do much damage I guess. I'm guessing that's what they suggest using when you tear a tank all the way apart and you don't want any trace of silicone left, because I was reading a 'build-your-own' thread. The alcohol makes sure the glass surface is clean and dry. I don't know if vinegar would do the same, I know it's great for removing limescale and calcium.

Floyd R Turbo 08-30-2009 09:34 PM

Chip under seal
Ok, so I started scraping off the silicone, and I found a chip in the glass on the edge of one of the side panes, about 1" from the top. It appears to have been chipped AFTER the original seal was placed, because it came off with the silicone. It's about 1/2 cm long and would be completely underneath the new bead, and only 1" below the surface of the water.

Anything to worry about? Besides making sure no air gets trapped in the hole?

h8z2luze 08-30-2009 09:53 PM

I just picked up some made by DAP from home depot it was kinda hard to find but it says its safe for fresh and saltwater fish so i got it.

Floyd R Turbo 08-31-2009 02:04 PM

Anyone want to weigh in on the chip? I just now got done applying the silicone, it wasn't as messy or difficult as I thought, except the tube was pretty hard to squeeze towards the end, hand got tired! I got he caulk worked into the chip pretty well so I don't think it will be a problem, but the fill test will determine! No I just have to wait a week.

mfdrookie516 08-31-2009 03:10 PM

i would let it sit for at least 48-72 hrs then put it in the garage and test it for a day or two... That would certainly beat having water all over the floor if the silicone doesnt hold... jmo tho

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