340 Acrylic Seam

[aotechs]

I broke down my 340 gallon tank for some much needed buffing and to make some changes to my sump. I noticed after refilling that it looks like there is one small craze or fracture to one of the seams. I cannot get a clear picture to show the details. Tank is built from cell cast, 1” side panels, and 3/4" front/back panels (used tank, don’t know why it’s built that way). Bottom is 3/8” and top is 3/4" (I added another layer of 3/8” material in a euro brace fashion to obtain the 3/4” thickness). Measurements are LxWxH, 84”x24”x39”.

On to the damage description and questions portion of the post. Imagine about an inch long craze that could be found on any panel and place it half way up of the left side front panel seam. The craze/fracture is running perpendicular to the vertical seam. I’ve had it full of water for three days and it has not changed in size at all. It doesn’t look like water is entering this hairline craze/fracture. The tank has a slight bow of 5/8” at the center so I don’t think deflection is the culprit. I’m leaning toward using some Weld-on 40 to reinforce the seams as a safety precaution. I have Weld-on 16 sitting on the shelf and could pool that into the seam instead if will work just as well. It seems that these two cements, possibly adding gussets also, are the most often suggested fixes.

All of my stock are in other tanks so time isn’t an issue. Any suggestions of which Weld-on product to use or personal experiences to share would be appreciated. If I’m overcomplicating things, should just let it ride, and watch the fish swim, go ahead and throw that out there too!

 

[wednesday13]

#16 is for "arts and crafts" imo... its brittle when it dries and actually weaker than the solvent based weld on #4. I used #16 for years before i knew any better and in turn watched it fail over more yrs...... From the sound of it it seems like ur seam is fine. "crazing" is micro fractures caused by bowing within the thickness of material itself. No way to repair it unless its re aneeled in an oven...looks like/resembles a shattered winshield. Seam seperation is just that..this will look white and is the 2 sheets seperating at the seams. Wherever ur seams are clear is where the glue is still bonded. Pics will def. help me determine if you need to reinforce the seam. If not its just a shot in the dark. weld-on #40 is great glue... the strongest option offered by weld-on for acrylic. Fairly easy to work with as a 2 part epoxy but the fumes are pretty bad. i recommend doing it outside or worst case sceario you open all ur windows and ventilate as best as possible for 24hrs. It also takes a full 72hrs to cure.

 

[aotechs]

Finally snapped a somewhat decent pic.

 

[wednesday13]

Nothin id be overly worried about... looks like normal wear and tear from all that water pressure at 39" height bowing. Def. keep an eye on it for spreading over the years. I dont see an immediate emergency tho. Any not so zoomed in pics lol? id guess the outside of the tank is on the left? ive seen chipping fractures like that many times on the outside edges... Looks like u do have a tad bit of crazing on what would be the inside of the tank. Thats from bowing. As the acrylic bends it makes those micro/spider fractures. Happens alot front and center on tanks also where the peak of the bow is. You can reinforce the inside seam with some 1/2"-1" square stock acrylic and weld on #40 if you wish, not a hard job. Depends if your more worried about looks or that bit of seperation spreading. Always hard to tell in pics. im not positive if that inside seam area is just discolored or seperated. Def. early stages of seperation, nothin crazy tho. Id guess ur tank is fairly new in my book around 10yrs old.

 

[aotechs]

OK, that makes me feel a little better. I was thinking to take the opportunity to reinforce the seams while it was broken down and this will be the deciding factor in doing so. I'll pick up some Weld-on 40 as suggested.

You're correct on guessing the tank age. It should be about 12 - 15 years old now. I'll grab a full shot of the tank sitting outside on a workbench for you later today.

 

[wednesday13]

OK, that makes me feel a little better. I was thinking to take the opportunity to reinforce the seams while it was broken down and this will be the deciding factor in doing so. I'll pick up some Weld-on 40 as suggested.

You're correct on guessing the tank age. It should be about 12 - 15 years old now. I'll grab a full shot of the tank sitting outside on a workbench for you later today.

Nice, a bit older than i thought. def in good shape then. acrylic still looks very clear. it gets a bit yellow after 20yrs. i have a cple over 25-30 over here still runnin fine lol... id prob go with somethin small like 1/2" square stock and the weld on #40 to keep it clean lookin. U can pretty much pour or brush on the #40 to ur square stock and stick it in place with a few pieces of tape to hold while it dries. Will probably hold up fine for many more yrs without doing anything but its also smart to be proactive. not as fun repairing them when u gotta tear a whole system down. ive done that many times by now aswell.

 

[aotechs]

I'll probably reinforce all four corners to keep it uniform. Also thinking about putting a layer of black acrylic around the overflow. I've never been a fan of the blue.

 

[wednesday13]

View attachment 1204469

I'll probably reinforce all four corners to keep it uniform. Also thinking about putting a layer of black acrylic around the overflow. I've never been a fan of the blue.

Looks like shes in pretty darn good shape to me! Thanks for the full tank shot. Def. debatable whether u need to do anything or not. Id prob. leave it be if it were my own... i run alot poorer condition and older acrylics tho.