Used 300 gallon tank has a broken bottom

[RecycledElectrons]

> Those existing glass strips really make it a much more difficult job. But still doable if you have the time and determination imo.

How do I remove the glass strips? If they were not there, I could fix it.

 

[Lepisosteus]

Agree with terrarium. Lot of work to get that thing back into decent condition

 

[Ulu]

. . . (2) in a 2.5 foot deep aquarium, the water pressure should be 72 pounds per square foot at the bottom. . . .

Not on the planet Earth sir. Water here weighs 62.4 lbs/cu ft
1.0ft deep=62.4 psf on the bottom
2.0ft deep=124.8 psf
2.5ft deep=156 psf

Still Not Much.

The first problem with patching is sealing to old silicone. You practically can't.

To make it seal without seepage, you must do a virtual band-aid seal over all the seams of the tank, after making the new structural bond to the patch, but before it cures too much.

 

[fishdance]

From your photos, it looks like they have added a bracing strip along the bottom. This is quite common as it doubles the bottom edge space to the vertical panes have more silicon contact.

It would be extremely simple to add an adjacent patch beside this bracing strip. Just clean the area with a sharp scraper & methylated spirits then firmly place your patch without squeezing out all the silicon. Do try to silicon all gaps as algae and mulm will get in between otherwise and be impossible to remove. Not dangerous but very unsightly and easily avoided. Your patch does not need to be one piece but for such a small area, one piece would be best.

For many longer tanks (10 - 12 - 16 foot or more) it is common practice to have a split bottom. This helps with flex supposidly (but could be a cost savng measure) and these are butt joined with silicon. You would be doing the same thing within the tank. Not much different to relying on silicon to water proof and hold the bottom and sides of tanks.

Also the CNC is a nice option but a $3 glass cutter would suffice if you want to shorten sheets of glass.

And if you do want to remove the existing bottom brace (I would not), just tape it with cloth tape and give it a few taps with a metal hammer so it cracks, then scrape out. The tape just to catch the shards better. Use a steel mesh fish fillet glove for protection if you have one. The glass will be very sharp.

At the end of the day, if you don't feel comfortable repairing the tank then don't.

 

[Ulu]

Almost anybody can do this work but it is a lot of work to get everything just surgically clean so that the glue sticks well. When I rebuild a tank I scrape the silicone off four or five times with fresh razor blades. I wipe it down with solvent at least three times, with clean cloth each time.

The wiping technique is important as well because you don't want to wipe stuff back and forth. As you clean the area, you wipe repeatedly in 1 direction with solvent and clean bits of cloth.

Some people use alcohol and some recommended methyl ethyl Ketone but I like acetone because it dries the fastest.

On the other hand you must work fast.

On repairs like these I would let the silicone rest a week to cure. It says 24 hours on the tube, but when building glass and aluminum windows in the shop, it was always at least a week before they went up on the building. When we built test windows for the test chamber, those windows were always allowed to cure for one week.

 

[fishdance]

The glass should be cleaned and dried but your description is quite a lot of overkill. A 300 gallon/2.5 foot deep tank isn't that large. Modern RTV silicons have come a long way and allow for a lot of errors. For a difficult patch, use a silicon with lots of stretch - flexibility (example a 50% modulus) so water pressure can self seal. But for this situation, any silicon would suffice. The cure time depends on the depth & thickness of the silicon bead and exposure to atmosphere so a week or more is good. Sometimes it can take several weeks.

Acetone can be used to clean glass but it does leave a residue (have a look with a flash light next time) so methylated spirits or iso propyl alcohol is best for deep tanks. Again for this particular situation, it won't matter.

 

[Ulu]

Okay, well I'll quit using acetone if you quit spelling silicone as silicon. Silicon is only one of the components of silicone.

(Almost any work with Spirits can leave a residue, and you have to polish the glass with a dry cloth until it's all gone. So far I haven't resealed a tank that leaked.)

One of the things that will Speed The Cure is to keep the humidity high during the Cure process. I will put a cup of water in the tank and cover the top with plastic wrap. I don't put it right on the silicone. But I live in the desert and it's very dry here so this helps me.

 

[RecycledElectrons]

I have been trying to separate the glass, but it is so tightly packed that I can not fit a razor blade between some of the pieces. I have repeatedly cracked reinforcing pieces by trying to work a putty knife along the gaps.

> 2.5ft deep=156 psf

Thank You.

> It would be extremely simple to add an adjacent patch beside this bracing strip.

I am concerned that the back bracing strip is not siliconed along its entire width. Instead, it looks like water can seep under the front 2/3 of it. (See pics.) So adding a patch would not stop water from seeping under the back bracing piece and out through the crack.

> And if you do want to remove the existing bottom brace (I would not), just tape it with cloth tape and give it a few taps with a metal hammer so it cracks, then scrape out. The tape just to catch the shards better. Use a steel mesh fish fillet glove for protection if you have one. The glass will be very sharp.

I will think about this.

> At the end of the day, if you don't feel comfortable repairing the tank then don't.

I may end up with a reptile tank.