FAQs on Acrylic Aquarium
Repair and Modifications:
Scratches, Pits, Stress Fractures and Crazing 3
Scratches, Pits, Stress Fractures & Crazing 1,
Acrylic Repair 1,
Acrylic Repair 2, & FAQs on Acrylic:
Drilling/Cutting, Construction, Solvents, & Glass A
& DIY Gear 1, DIY
Gear 2, Tanks, Stands, Covers,
Custom Aquariums, Stands,
Acrylic Aquarium Repair 4/15/17
Hello there and thanks for providing such an informative website! I purchased a
used acrylic tank whose condition is a bit rough, it’s 150 gallons 72”x24”x20”
3/8ths thick sheet pretty standard stuff. Anyhow I could really use an expert
opinion on whether this tank will require dowelling after I re-solvent the
separated chemical welds.
<Yes; I would apply doweling here. My rule of thumb is anytime, with the whiting
out anywhere, that more than half the joint is troubling... to do so. Plus the
nearby crazing worries me.>
If so must I use cast acrylic or can an extruded rod be utilized for the
<Either will be fine here; for this application.>
Furthermore when do you recommend using weld-on 3 versus weld-on 4 for
<Both are close to being about the same viscosity. I like "runnier" for tight
areas, brand new material in general>
The enclosed photo is of the front upper left corner, and is by far the worst
corner of the aquarium the rest of the tank is surprisingly not so bad. Thanks
for providing information that allows a regular working guy to afford his dream
aquarium! Thanks David
<Welcome! Bob Fenner>
Re: Acrylic Aquarium Repair 4/16/17
Hi Bob thanks for getting back to me so fast, in your response about
dowelling the corners you mentioned the near by crazing worried you
<Evidence of stress there... could be from poor matching of joints, uneven
stand, weak acrylic.... But points to the need to add the doweling>
With the additional dowelling should I worry about the crazing?
I thought it was minor you can't feel it at all, but then again I’m no
Acrylic tank repairs
Hi guys, I have a question or two for you all. I bought a old 8x2x2 tank off
Craigslist for cheap.
<Ahh; an olde stock 240>
The tank was pretty rough when I got it. The top brace was cracked all around
one of the opening on top which I patched with Weldon 16 and another piece of
I'm not sure if the tank was made of acrylic or Plexi or??
<Both common names for the same compound... though "qualities" vary>
Anyhow, the top had 4 access holes in it. The people before me had cut the top
brace within a 1/8" to the back panel and did a terrible job. They did this on
both sides of the tanks and said it was because they used to have a hob filter
<Still; not a good idea>
Because of this the tank had some bowing in these spots while dry.
Before I read this site I went ahead and used large clamps to pull it back to
normal and used Weldon and patch to secure it, is this going to be OK?
Also there was some crazing along the back pain Seams so I used Weldon 16 to add
on a 3/8 square dowel in the seams with crazing will this help?
<Not likely; no. The crazing is permanent>
If needed I can send pictures. The guy I bought it from said it never leaked but
I wasn't convinced even though he seemed pretty honest. Any suggestions would be
<Enjoy your new tank. It appears you're aware of the most important/dire issues
and have addressed them. Bob Fenner>
Crazing in acrylic front panel
Hello crew, first thanks for this valuable support and resource you provide.
I have a 55 gallon unknown brand acrylic in the living room that has
crazing in front panel, normally you cannot see it except at certain angles
or/and when the fish reflect the light.
< Well put>
The crazing appears to be increasing over time both in surface affected and
I am concerned about whether it is safe to continue using it or if there is
a risk one morning we may wake up to a flooded living room.
Is there anything i can do to prevent/ mitigate its progression?
<Mmm no; but this crazing; failure is not "that bad" as yet. I would keep
using this tank for years to come>
I do weekly large water changes (about 60% of water), do you think this
might be causing or contributing to it?
<Not much, no>
<Welcome. Bob Fenner>
Acrylic Tank - Crack or Crazing?
I do keep up with the questions and comments on your site but I have a tank
that has stumped me, as well as, my LFS. I have included two photos of the
area of the tank, which is a 55 gallon acrylic hex. The long issue is not
growing, the shorter one is slowly growing downward. If you enlarge the
first one, you can see the details of the cross scratches, or whatever it
<Crazing.... due to poor material... IF you want to use this tank as an
aquarium, I'd drain it and solvent a panel over the bad one (on the
outside)... W/ Weld-on.... turn the bad panel to the wall>
The second one shows more of how it looks in general. In order to show the
area best, light was turned off and daylight is coming through. My
LFS says the manufacturer should be contacted to see if this tank is
<I would drain it for now; but yes>
They have never seen anything like it before and have no idea if it is a
crack or some kind of crazing. I don't know which manufacturer built this
tank, as the label was missing when I purchased it second hand.
<They won't warrant it then>
I can feel the cross scratches in a couple of places along the line. Please
let me know what you think about this issue and what you suggest I might do
to fix it, if it is fixable. Thank you.
<As stated. You can use thin material, colored...>
Crazed; tank... 12/15/15
I just got my first "large" tank from craigslist. Bought a complete system with
a Tenecor 55 gallon acrylic tank, the tank is probably over 10
years old and other than some bowing in the front (even empty) seemed in pretty
good shape. I had no idea about acrylic tanks and what i should be looking at. I
did some research on polishing and spent about 20 hrs working on
polishing, now looks really good. But I didn't know anything about what
I should actually worry about, tank integrity.
<A bunch re this archived on WWM>
I'm really concerned about the top front seam in the center of
the larger openings, there are several hair thin cracks and yesterday while
filling the tank to the top I heard a couple of cracks and it seamed one
or two of the cracks got a bit longer (now reaching through the seam width).
<?! I see the crazing, but not cracks....>
I really like my new tank and put a lot of work into it, but I'm concerned about
the top seam failing, the rest of the seams seem to be almost with no cracks.
Any help would be appreciated to answer these questions:
Is it safe to use the tank as is?
<Likely so.... that is to say/state, that knowing Tenecor (they're out
of biz now a few years), and having been a fabricator... the blems are not so
bad here... that I would use the tank (myself) as is>
Can it be fixed and in that case how long may it last and how safe will it be?
<The crazing? No; can't be fixed. Not problematical if all (the tank, stand...)
is set on a support that is strong, level AND planar. Again, gone over and over
on WWM. Try the search tool (on every page, sigh...)>
I've been reading about using a 1/2" square or triangular acrylic rod welded to
the corner but i have not been able to find any details on how it should be done
and what type of materials should be used, lots of discussion about WeldOn 4 vs.
16 and extruded vs. cast rods (along with triangular vs. square) but no definite
answers on what should be used or how it has to be done.
<See WWM Re. For a 55 in the apparent condition here... I would use as is>>
Thanks in advance for any information/ opinions you may share...
<Welcome. Bob Fenner>
Thank you so much for your quick response, I did read a lot of WWM over the
weekend (after the fact...) but I wanted to try to have your opinion since I'm
totally new to this. By your answer and given the limited information that i
have given you it seems like it would be safe to use as is, correct?
Sounds like it's not needed/ worth the effort to weld a reinforcing rod and I'm
concerned about making things worse given my lack of experience.
<The solvent can be a mess>
Is it normal to hear a couple of cracks when filing it to the top?
<No; not normal... NOT>
Any further/ periodical inspections i should do or any red flags i should be
<I'd practice fill outdoors...>
Thanks again for your help. I'll definitely use the info in WWM to set up my
Crazing or scratches?
I hope I’m emailing the correct address. I was reading a lot of the other issues
with acrylic crazing, scratches, etc. Wondering what you though of my issue.
<Thought? From your too-large file pic, it appears you have a bit of both. Just
read on WWM re how you might fix the scratches. Naught you can do re the crazing
that exists... preventing further... might involve making sure the tank is on a
level AND planar stand>
I bought a 10ft by 2ft by 2ft used acrylic tank off craigslist. It had it’s fair
share of scratches. I took the time and research and restored the acrylic. When
I first filled this tank after installing in my house everything looked amazing.
No scratches except for one minor spot where a piece of driftwood hit. I noticed
after cleaning with an acrylic MagFloat some long scratches in a certain area.
Now I’m freaked out to use the thing and clean everything with a microfiber
cloth and a non stick scrub pad, which I was also scared to use but website
forums swore by them and it works great.
My real issue now is over just a few months time, I have a lot of little specs
or scratches all over the outside of the tank. I’m fairly certain this is on the
outside. However I can’t feel the scratches on the outside or inside when I run
my finger over it. They appear on the same plane as the larger scratches and I
can see a few minor scratches on the inside that I can feel with my finger nail.
I can tell they are on the inside of the tank compared to these.
That being said I was confident in buffing these scratches out again. I started
out with Novus. No luck. Then 2000 grit sandpaper. No Luck. Then took a whole
morning with 400, 600, 800, 1000, 2000 grit sandpaper, Novus, and a buffer
cutting pad and polishing pad using Meguiar's M105 Mirror Glaze Ultra-Cut
Compound - 32 oz. and Meguiar's M9 Mirror Glaze Swirl Remover - 16 oz. Same
process I used when buffing everything out before.
<Some work now; no fun>
Still no luck in making this look better. I’d say in 2 months time this went
from nearly perfect to about a 6 foot section of small marks like the pics show.
Couple other quick notes. The long scratches you see appeared first, presumably
from the Mag float. All the small specs appeared slowly over time. I can’t see
the marks if I change my viewing angle. It’s the worst when staring straight at
eye level. Is this crazing?
<Some appears to be>
Should I be concerned? I’ve only had this filled up since June. Thank you for
<Again; the stand issue. Oh... for those of strong constitution (and
experience), there are heat application techniques. I'd be consulting with a
company that does this work. You can find these on the Net. Bob Fenner>
The new series within LA Fishguys, Aquarium Tech Talk
The newest of LA Fishguys, and a first for its new series Aquarium Tech Talk,
Episode 149 shows the polishing of scratches in a large acrylic aquarium, still
full of water.
<Ahh; a very valuable topic. Will post, share. BobF>
Your promotion is in Part 1
Part One https://youtu.be/Y8eTWZSNLWM
Part Two https://youtu.be/dXthrMx7sq4
Jim Stime, Jr
Aquarium Design - Installation and Maintenance
Midwater Systems - JELLIQUARIUM Jellyfish Display Systems
MyFishTank.com - Acrylic Aquariums, Stands and Canopies
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