# Neat silicone fillets in a diy glass tank



## k7gixxerguy (Jan 12, 2012)

Ok, so I built a 67 gallon tank out of 10mm in January, last weekend it started leaking while I was away and left all my cichlids dead. Thankfully it must have dropped to the substrate level shortly before I got home as I was able to save my three synodontis lucipinnus. It had a very slow pinhole leak when there was no weight of rock and substrate on it. The only explanation that I have found is that using masking tape to make sharp crisp lines when smoothing the silicone can leach the adhesive under the silicone and lead to a leak. Obviously I want to make sure that this doesnt happen again. What does one do if you shouldnt use masking tape to get nice silicone lines? I used aquarium specific silicone before but will be using GE Window and Door I this time around.


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## Deeda (Oct 12, 2012)

I no longer use masking tape when re-siliconing used tanks. The key is to cut the nozzle tip to the appropriate size so the bead of silicone, when applied and tooled with your finger, is the correct fillet for the tank you are repairing.

If the bead is too large, when you tool the silicone, it makes too wide of a fillet. The reverse would be true if it's too small. In that case the fillet won't make good contact to the glass panes.

I find it easiest to practice the bead size before actually doing the job. Cut the nozzle tip smaller than you think you need when you first practice. You can always cut it larger if it's not sufficient to make the proper size fillet.


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## k7gixxerguy (Jan 12, 2012)

Deeda said:


> I no longer use masking tape when re-siliconing used tanks. The key is to cut the nozzle tip to the appropriate size so the bead of silicone, when applied and tooled with your finger, is the correct fillet for the tank you are repairing.
> 
> If the bead is too large, when you tool the silicone, it makes too wide of a fillet. The reverse would be true if it's too small. In that case the fillet won't make good contact to the glass panes.
> 
> I find it easiest to practice the bead size before actually doing the job. Cut the nozzle tip smaller than you think you need when you first practice. You can always cut it larger if it's not sufficient to make the proper size fillet.


ok, what would the best size be for 10mm glass? 48" by 18" by 18" tank. Also do you use a gloved finger or an actual tool?


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## stu1982 (Jan 16, 2012)

Make sure your finger is moist when you run it along the silicone and dont use too much pressure otherwise it will push the silicone out to the sides. If you find a lot of silicone is building up on your finger gently pull away, clean it off and run your finger back up the joint. Practice is the best thing, if your planning a sump aswell try building that first as it'll give you lots of practice.

Good luck.


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## Deeda (Oct 12, 2012)

I cut the nozzle so there is a 3/16" hole in the end when I did my tanks. I also cut the tip at an angle.

I wear viny gloves when applying the silicone and also to tool the bead + wipe the silicone off the gloved finger before tooling a new corner bead and if excess builds up on the gloved finger. This helps to keep the tooled silicone cleaner looking.

Don't worry about any smears you may get on the glass. You can clean them off with a razor blade AFTER they dry.


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## theoryguru (Oct 11, 2011)

+1 new blades and latex gloves - key for a project like this.


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## TheOriginalFuzzy (Jan 25, 2012)

I use masking tape with no leaks... But, I am anal about cleaning the joints with rubbing alcohol and allowing to dry before applying the silicone and I remove the tape as soon as I finish running my finger up the bead... There are probably many different ways around it but the most important factor is making sure that the glass is super clean...


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## 123vb123 (Feb 10, 2012)

lol....

This is what i do when i build tanks (and i have build alot.)

1. Get silicone
2. Empty the bottle anywhere in the tank
3. Stick your hand init and place the silicone everywhere needed.
4. Get a any object to scrape off unwanted chunks and remnants.
5. Let it dry
6. Your done, easy as fawk.

however im sorry to hear you have to re-do everything, water on your floor, and dead fishys!


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## BillD (May 17, 2005)

A few things to consider. A properly built tank doesn't need an inner fillet. I was looking at some nice starphire nano tanks a couple of weeks ago, and they have no inner fillet seam. The use of masking tape is open to debate. it isn't on very long, so I can't say how it will affect the seam.the size of the seam isn't really relative to the thickness of the glass. You really are only trying to cover the butt joints between the panes in case there are any voids from the construction. having a fillet that is too large gains nothing but makes it harder to finish. there should be no air beneath the fillet, so care must be taken when applying and smoothing. The fillet needs to have enough pressure to smooth evenly, feathered to the edges.
The glass need to be scrupulously clean. A serious cleaning once the old fillet is removed and a final clean of the seam area with alcohol or acetone prior to adding the silicone to remove any oil residues from your hands. With a little practice, a nice, even, and smooth bead can be applied without the use of masking tape. As recommended by McDaphnia, a cardboard box and cheap caulk can be used for practice. As well, a dry run of the actual caulk application, immediately prior to application, so you can do it quickly and smoothly is a good idea. With large tanks, a helper to help you roll the tank can make the job easier than trying to do it in one position.
As to the original post, I am curious as to how the tank was assembled, as it is stated that without the weight of substrate and rock there is a pinhole leak. Is the bottom somehow suspended?


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## k7gixxerguy (Jan 12, 2012)

BillD said:


> A few things to consider. A properly built tank doesn't need an inner fillet. I was looking at some nice starphire nano tanks a couple of weeks ago, and they have no inner fillet seam. The use of masking tape is open to debate. it isn't on very long, so I can't say how it will affect the seam.the size of the seam isn't really relative to the thickness of the glass. You really are only trying to cover the butt joints between the panes in case there are any voids from the construction. having a fillet that is too large gains nothing but makes it harder to finish. there should be no air beneath the fillet, so care must be taken when applying and smoothing. The fillet needs to have enough pressure to smooth evenly, feathered to the edges.
> The glass need to be scrupulously clean. A serious cleaning once the old fillet is removed and a final clean of the seam area with alcohol or acetone prior to adding the silicone to remove any oil residues from your hands. With a little practice, a nice, even, and smooth bead can be applied without the use of masking tape. As recommended by McDaphnia, a cardboard box and cheap caulk can be used for practice. As well, a dry run of the actual caulk application, immediately prior to application, so you can do it quickly and smoothly is a good idea. With large tanks, a helper to help you roll the tank can make the job easier than trying to do it in one position.
> As to the original post, I am curious as to how the tank was assembled, as it is stated that without the weight of substrate and rock there is a pinhole leak. Is the bottom somehow suspended?


As far as construction, yes the bottom is suspended inside the front back and side walls. I ordered plastic rims that have grooves for the four verticals and that puts the bottom sitting on flats. So it is somewhat suspended when its all said and done. I think for safety sake this go round I will put some styrofoam or something under the two large flat sections as the top and bottom rims are identical with a brace through the center. I can take a picture of the top rim if that would help get the idea across.


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## BillD (May 17, 2005)

My personal preference is for sides on bottoms builds. having a plastic frame doesn't negate this method. The suspended bottom is supposed to allow the tank to better withstand torsional forces. It may seem easier to assemble a tank this way, but making sure the edges of the bottom are coated with silicone is imperative, as you have found. In this case you have 2 failures. the inner seal failed, which allowed water to get to the void created during the build. I had a similar issue with this type of tank (Hagen brand, 30 gal) I resealed and 3 weeks later a bigger leak than when I started. I removed all the silicone I had added checked to find the leak, and saw that there was a sizable area of failure. So, I removed the bottom and re did the inner butt. It was not an easy task to get the bottom out or ensure the silicone was going to fill the gap all around the bottom evenly when I put it back. That was a couple of years ago, and it is still going without issue.


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## k7gixxerguy (Jan 12, 2012)

BillD said:


> My personal preference is for sides on bottoms builds. having a plastic frame doesn't negate this method. The suspended bottom is supposed to allow the tank to better withstand torsional forces. It may seem easier to assemble a tank this way, but making sure the edges of the bottom are coated with silicone is imperative, as you have found. In this case you have 2 failures. the inner seal failed, which allowed water to get to the void created during the build. I had a similar issue with this type of tank (Hagen brand, 30 gal) I resealed and 3 weeks later a bigger leak than when I started. I removed all the silicone I had added checked to find the leak, and saw that there was a sizable area of failure. So, I removed the bottom and re did the inner butt. It was not an easy task to get the bottom out or ensure the silicone was going to fill the gap all around the bottom evenly when I put it back. That was a couple of years ago, and it is still going without issue.


I didn't want a suspended bottom but when the plastic came in it was designed for this method. I thought that it actually was harder to do in that it is more difficult to get a good butt seal while sliding glass down into this frame. Lesson learned and I will just make my own trim for my next tank. Should I be concerned with having a lot of rock in this tank again? I pretty much filled the area in the plastic effectively making a full outer seal as well this time.


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## BillD (May 17, 2005)

I believe if you are going to do a suspended bottom in a frame, the sequence is back, bottom, sides, front.


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## BillD (May 17, 2005)

I rethought and perhaps the easier sequence would be bottom, ends, front, and back.


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