Glass cracks, old silicone - which of these are fixable?

[UrbanDryad]

I get my tanks second-hand. They often need cleaning, and sometimes repairs. I'd like some opinions about what I can do with the following bits and pieces.

1) Superfish Scaper 45. It had a few chips on the corners when I got it, but after cleaning it, I noticed this crack in the glass. It might have been my fault, I'm not sure whether it was there before. I'm doing a water test now, but I'm not optimistic. When I press on the smaller bit of glass from the inside, I can hear noises, so it's clearly not going to withstand the pressure of 45 litres of water. So... silicone it back together and hope, patch it with a small piece of glass on the exterior, or deconstruct it and replace the entire pane and then put it back together? Or would it be possible to just fill that corner of the aquarium with expanding foam / silicone and keep it away from the water pressure entirely? I really wanted to get this up and running so I'm quite frustrated at the idea that I might need to find an entire replacement pane before I can start planting it up...

2) Clearseal 16L. It's got a bunch of chips around the bottom edges. Are these likely to be a problem for the structural integrity? I was planning to silicone it to a thick foam underlay and add trim around the bottom edges, so they'd be packed in quite firmly by other design elements.

3) Juwel Primo 54L. The silicone connecting two panes of glass has some damage to the external part of the bead. It's held up to one overnight water test, but is this doomed in the long-term? In most advice about resealing aquariums, they differentiate between the bead of silicone used to attach the panes together, and the bead used to ensure the inside is watertight. They say that when resealing, you can remove the internal silicone without deconstructing the whole tank, so long as you leave the attaching bead in place. However, in this case, there's just the one attaching bead (see first picture below). So if I wanted to reseal it, would I cut off the internal parts of the attaching bead in order to add a new sealing bead? Or should I just take the entire thing apart and reattach everything with new silicone?

4) Unknown 40L. This has the same bead structure as the above Juwel one, but it looks like the outer part of the bead has been sliced off, so I'm sharing this partly as an illustration of a counterpoint - if this tank works as-is, maybe the missing segment of external bead on the Juwel is no big deal? I also have a potential issue with it, though - see second and third picture below. One of the panes looks weirdly offset - kind of an unexpected gap between the two panes of glass, filled only by the silicone. I'm wondering if this will be a long-term structural problem?

Thanks for reading, and thanks in advance for any advice. Also, if you've got recommendations for forums / online spaces where there's a culture of regularly reconstructing / resealing tanks, I'd be grateful for that too! There seem to be a lot of places where the advice is just "don't do it, buy a new one" even though it's definitely possible. (I'm a fan of Serpa Design, I've seen him rebuild / reseal a whole lot of old glass tanks!)

 

[PARAGUAY]

It's difficult to assess chances of success off photos. Whatever you try, silicone, use the best quality one specific for the purpose it used to be Dow Corning ,no idea now, there are a few UKAPS members who have done successful repairs to damaged tanks hopefully they will see the post. If all else fails and you don't trust the volume of water how about terrarium?

 

[dino21]

1. Would place the patch on the inside of the tank so the water pressure is pushing it up against the original glass, if on the outside its going to push it off easier.
2. Difficult one and on a bigger tank would say replace the bottom sheet, but for just 16ltr would just smooth off those rough chips .
3/4. Just depends on your set up and how bad would a leak be ? if you have the time then we would strip it down cleaning off all the silicone and resealing.

Always use the BondIt HA6 silicone, just a case of finding a supplier with good fresh stock, not out of date.
When at the local glass merchants, always ask them for some of their worn out diamond sanding discs /cloth which for the diyer still has some useable life left.

 

[UrbanDryad]

Thanks both

The silicone I've got is Everbuild AquaMate Aquarium Sealant - I've used it before without problem, but only on a tank I was turning into a terrarium. (It had glow-in-the-dark silicone sealant, so I replaced it with something a bit less lurid). Is the difference in quality so significant that I should avoid using it?

If all else fails and you don't trust the volume of water how about terrarium?

That was originally my plan! I got into aquariums via buying old tanks to use as terrariums, but I'm falling in love with the aquatic side of things, so I'm increasingly keen to see which of these tanks will hold water.

1. Would place the patch on the inside of the tank so the water pressure is pushing it up against the original glass, if on the outside its going to push it off easier.

Very good shout! It failed a leak test pretty quickly. I had a browse online and getting a new pane doesn't seem like it would be too expensive, plus if I decide to use it as the back panel I don't need to worry about getting low-iron. I'll call up some local glass places during the week and see what they can do for me - if I can replace the pane for a reasonable price then that's probably the most sensible thing to do, rather than patching, right?

2. Difficult one and on a bigger tank would say replace the bottom sheet, but for just 16ltr would just smooth off those rough chips .

Is that for aesthetic or structural reasons?

3/4. Just depends on your set up and how bad would a leak be ? if you have the time then we would strip it down cleaning off all the silicone and resealing.

Number 3 has now been cleaned again and stood up to another overnight leak test, so I'm feeling a bit more confident about it now. Number 4 is now being tested for the first time. My instinct was to say that yes I've got time to strip it down and redo, but actually, this month is manic for me and I've been unwell for a chunk of it, so maybe I don't have time, and should just aim to get things set up and cycling ASAP and deal with leaks if they happen / upgrade later.

Always use the BondIt HA6 silicone, just a case of finding a supplier with good fresh stock, not out of date.
When at the local glass merchants, always ask them for some of their worn out diamond sanding discs /cloth which for the diyer still has some useable life left.

Thanks for the tips

 

[jaisol]

Silicone does not bond well to old silicone, try to clean as much as possible off. Spread it over / past the old line of silicone
Bottom cracks I have sandwiched them with 2 thin 2-3mm glass, one on the inside and a full sized bottom piece on the outside.
Chips I tend to ignore, or pull them out and blob silicone in the hole.

Silicone does not work well with plastics eg lexan.
Cleaning .Not many solvents work well about the best I've found is acetic acid / vinegar, and that was dipping the glass for a few days in it.

 

[dino21]

Is that for aesthetic or structural reasons?

For safety - too easy to catch your fingers on those sharp chipped edges , could cover with silicone instead.

Silicone does not work well with plastics eg lexan.
Cleaning .Not many solvents work well about the best I've found is acetic acid / vinegar, and that was dipping the glass for a few days in it.

After removing as much silicone from the glass with a good blade, usually find wiping it with a cloth soaked in White Sprits / Turps a few times gets the remainer off, but you must wash off any trace of the turps before using new silicone !
Not used it on any glass yet, but had to remove a lot of old sunbaked silicone from some upvc boards and found this Remover certainly helped soften/release the silicone and so easier to remove.
No Nonsense Sealant Remover 100ml - Screwfix

 

[UrbanDryad]

... belated thanks for your comments, and sorry I fell off the forum for a while!
I've finally attached a new panel of glass to the Scaper 45, and I am worried that there's somehow gaps in the silicone - these weird white/silver bits look to me like they might be air bubbles or something. Have I screwed this up? Obviously I'm planning to water test once it's had time to cure, but I'd appreciate insight about how to interpret these
Second picture shows the silicone bead before I put the tank onto it, in case that provides any clarity - the white/silver bits are on the left side, just below the corner.

 

[MartyK]

Best to wait and see how it performs with a water test. Take note of any changes to those spots whether they get larger or smaller.

Are the spots located where you first started applying the silicone to the glass? It's possible they are from the silicone 'skinning over' after having been exposed to the air for longer than the rest. Silicone does have a fairly short working period in order to get the most strength and that's why you'll often see folks inject the silicone between two already assembled panels as it immediately touches the two areas it needs to bond to.