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Discussion Starter · #1 ·
So I have some crazing happening on the bottom of my 55g Truvu. I did not notice these when I got the tank off craigslist but now they are pretty apparent. I a general "meh, its acrylic and its fine" sentiment on other forums but I am not sure about it in this case as these are a bit deeper. It held water fine for 24hrs and they are in the middle of the bottom pane. The worst one is about an inch and a half by about 1/8th inch deep. Is this something that is going to give out sooner rather then later and is using weld-on to seal the crazing a bad idea?(Ignore the latex paint, I set it on the stand a little to early.)
 

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plastics can be so weird.. bought a little clear measuring cup the other day for use in the kitchen... every time I put cold milk in it, it would craze so badly, you can hear it crackle like rice crispies..
 

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Buff it out baby!
 

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Look at the big mark, it is clearly a craze, and goes quite deep. My money is on the thickness you see there is actually the depth.

Yup, there is no width to them, you can't feel them at all, the picture was at an angle so they show up better. Also milk crazing acrylic... "Now fortified with windex!"

So my girlfriend works at a machine shop and their acrylic engineer stopped by, he looked at the pictures and said its pretty much nothing you can do, and its mainly cosmetic and nothing to worry about.
 

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The questions to ask yourself are, how would I feel if the tank failed, and it dumped everything on the floor? Also, could I sleep at night knowing that the plastic might fail, even though it's unlikely?

If it's going to really bother you, replace the tank, rather that trying to use it.

That being said. I don't think you'll have a problem.
 

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Discussion Starter · #8 ·
You have a point, to be honest insurance will cover the water damage, I would be more worried about saving the fish. But it sounds like its rather unlikely there will be issues.
 

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if its the bottom pane, dnt worry too much as long as your stand is not hollowed and have a flat surface.. worry about the crazing along the seems
 
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I don't own an acrylic tank nor do I have experience with them, but I do know that unlike glass tanks, acrylic tank bottom need to have 100% of its bottom supported. If you are diy-ing a stand, I would over build it to beef up the support to have it be as structurally sound as possible. Some put a filler such as styro foam, insulation sheet or even a yoga mat underneath. This filler compensates for any imperfections in the stand itself to get you that 100%. I actually had to do this with my glass tanks on my diy stands due to slight imperfections in the plywood. Otherwise I risk having corners/edges not supported that could cause stress on a seam somewhere. I lost a seam on a 55gal once because the stand warped and a seam gave way.
 

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As a Plastics Engineer, I can share some basic guidelines to potential fracture.
Surface scratches are cosmetic, and normal for acrylic. If any of those scratches begin to deepen, it's the most predictable place for crack propagation and failure. That deeper scratch that you mentioned is the one I'd be most concerned about. If it widens at all it will eventually keep going with any applied stress (like a car windshield that gets attacked by a rock). This is due to the sharp notches that are now there on each side.
If you can buff it enough to round out the edges of that crack, it re-concentrates the stress over a larger area taking the pressure off the points that want to grow.

If you are willing to take a gamble on it, which it sounds like you are, measure it's length, and then periodically measure it again for comparison. Maybe insert a 2-3" piece of PVC pipe over that area so the substrate doesn't cover it right away. The ultimate test is how it performs with the extra weight of a complete tank. If it grows (even slowly), it's your sign to shop for a replacement tank.
 
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