Leaky 300 gal. – 09/17/07
My name is Joey and I have a very important question. First, I would like to say love the web site. I wish they would stop making 10 and 15 gallon aquariums come on that is not a home!! Bigger is better I am going to look at a 300 gallon tank for sales that has very thing included. But it needs to be resealed. Is it worth resealing? I have saved some fish from people that could not maintain the demands of a growing fish. And they need to be moved to bigger tank I don't mind trying I am just worried about the pressure that comes with a three hundred gallons of water, rocks and a two foot long Pacu and a Giant Gourami. If the answer is yes what is the best resealer and where can I buy it? Thank you.
<Greetings. Thanks for the kind words, and while I agree 10-15 gallon tanks aren't ideal for many people, especially beginners, they're very useful for those of us who like breeding fish! But I agree, the "best seller" starting tank should be a 'long' 20-gallon tank. Now, repairing a tank can be done. There's an FAQ and links to all kinds of articles here: http://www.wetwebmedia.com/aqrepairfaqs.htm . But, the bigger the tank, the more difficult this becomes and the more important it is to get right. Personally, unless I was experienced with fixing small tanks, I wouldn't take the chance with a 300 gallon tank. As you say, that much water is a lot of pressure, and when such tanks fail, they can do explosively. Aquarium sealant is silicone and you can buy it anywhere that caters to fishkeepers. It's important to use the right kind though; generic silicone is treated with chemicals for use in bathrooms and around the house safely. You want the proper aquarium-grade silicone. Quite possibly, you'll make life easier getting the leaky 300 gallon tank, stripping it of parts, and then using them on a new 300 gallon tank. As a rule, the tank part isn't terribly expensive compared with the hood, cabinet, lights, filter, etc. Cheers, Neale>

1" thick acrylic - Can we fix it?  9/27/05
Hello, I couldn't find a similar problem to mine  except ...leak leak... leak. I have a very large 500+ gallon tank. It's 1" baked  acrylic on all sides. I have saltwater in it and have had it for like 6 - 7  years. It's completely built in to a wall and is supported on a steel structure.  We noticed some water damage on a piece of quarter round that was trimming it  and when we removed the trim water started spurting from a pin hole leak. The  trim was actually holding it in check some what. I don't want to try and remove  the whole tank from it's location as it will cost major in carpentry. Will this  acrylic cement (northcoastmarines)
work for this type of leak? How does this  type of thing happen after all these years?  Kim
<This tank can likely be repaired... in place. Do look into square "doweling" (this is sometimes only flush/ninety degrees on two of the four sides... You must make sure the flush sides are affixed to the corners. What needs to be done? Drain, clean the tank entirely, cut the doweling to size to fit in all corners (yes, including the sides), and solvent in... The extra bit of acrylic in the corners won't be obvious in time. Cheers, Bob Fenner>

Re: 1" thick acrylic - Can we fix it?  9/30/05
Thanks so much but where does one find square acrylic (I assume not just plastic?) "doweling"? Kim
<Should be available, as well as solvent/Weld-on and cleaner from a large/r plastics distributor in your town... or mail-order... Use your "Yellow Page" directory, the Net to find. Bob Fenner>

Cracked acrylic tank  9/20/05
Well Bob,
You were right, only give it time....I've got a new one for ya.
My crew and I were installing a new 36" x 30" x 36" acrylic tank from AAT today.  As the tank was being set down on the floor, one of them lost their grip for fear of getting their fingers pinched.  The right front corner of the tank hit the bare concrete floor from about 2 inches up....that's when I heard that unquestionable cracking sound.  I saw my profits disappear before my very eyes.  However, upon inspection, it wasn't nearly as bad as I thought.  The crack is actually in the bottom plate about 1/4" in just beneath where the front panel (front and sides are one piece with bent corners) is welded to the bottom panel, about 6 inches from the start of the right corner radius. This crack extends from the bottom surface upwards about 3/4" in an arching pattern, almost like a rainbow...but not nearly as pretty, and finishes back at the bottom surface. Its a pretty clean crack and does not go anywhere near where there would be water.  I figured that because it directly underneath the front panel, that even if it extends further over time, it would eventually dead end into the front panel and because its almost dead center under the front panel, that there would be plenty of material to keep it from leaking.
Your thoughts on this ????
Scott C. Wirtz
>>>Greetings!
Sorry it took so long to get back to you, things are crazy for many of us here on the "crew" and tons of queries coming in.
Bottom line, it's impossible for any of us to say for sure about your tank. I had a similar thing happen though to a 300 gallon tank, and it was just fine.
Good luck!
Jim<<< <<RMF would still run a bit of Weld-On (of lower viscosity) into the cracked area>>

Need advice on separating acrylic sheets...  8/27/05
Hi Bob,
<Ed>
My name is Ed Ruiz. I'm in SLC, Utah. Seeing your vast experience in the hobby and working with acrylic I hope I can get some advice from you.
<I see>
I recently acquired a lot of 1/8 and 1/4" acrylic sheets (24"x48") that had apparently been stored under less than ideal conditions. I find that the sheets are still with their paper masking on, but between each two sheets there is a yellow or blue textile material that is holding them together. My theory is that they were heavily stacked (too many sheets atop each other for a long period of time -
<In the heat...>
I got them for free) and the masking textile's adherent has bonded rather strongly. I have not insistently attempted to separate the sheets and would like your opinion, advice or suggestions. I will use the sheets to build aquariums for a hatchery project I am working on.
Ed Ruiz
<Very hard to separate... inserting long, thin metal strips between and prizing apart is likely your only option... though this will very likely scratch through the protective masking... Have you tried speaking with folks in the acrylic business? Manufacturers of such do have websites... I would get their input before proceeding. Bob Fenner>

Re: need advice on separating acrylic sheets...  8/30/05
Thanks a lot Bob, your suggestion is exactly my wife's' and makes sense.
<Ahh, good company>
As to the acrylic manufacturer's or vendor's websites, they're more interested in selling me a product for taking the paper masking off. This tells me they did not pay much attention to my enquiry in the first place.  
I'll go with your advice.
Ed  
<Please make it known how this goes... Years back I tried to do this... with piano wire and a strong friends co-help, jamming thin metal strips twixt the sheets... and getting the old masking off... what a lot of work besides! I would listen to the acrylic manufacturer's, distributor's advice re this. Bob Fenner>

Acrylic crack repair, opportunistic/typical Moray behavior  11/11/05
I just bought a used 55 gal hexagon acrylic tank.  I was moving it around trying to determine placement when I realized there is a crack in the top panel.  No point in finding blame now, I just want to know if I can save it or take this as a loss.
<Mmm, can likely effect a simple repair here>
The crack, definitely not crazing since I can feel a separation, starts from a corner round of the large cutout and extends about 3 inch toward one of the six sides.  One more inch and it is going to hit the side edge!  I've been reading about using Weld-On and applying an acrylic panel to the crack.
<Yes>
Also is drilling a hole at the end of the crack going to stop it?
<Not likely useful, necessary>
Can I get Weld-On at Home Depot if I were to try this?  
<Best to seek out from a "Plastics" supply... look in your local Business Yellow Pages Directory re>
Should I worry about this crack since it is only on the top panel?
<Mmm, not much to worry about, but I would solvent it closed>
The tank is a standard 55 gal hex 24x24x28.  It's funny how things go wrong and just seem to spiral even more.  I bought the tank intending to make it a new home for my white-mouth eel about 15in, who has managed to eaten two smaller fish.  Well he attacked and ate my 6-7 inch lunare wrasse last night.  I couldn't believe he was able to swallow the wrasse or even catch it.  What a sight! Thanks
<Welcome... an easy project/fix... Bob Fenner>

Repairing acrylic leaker 3/7/06
Hello,  We are searching for someone who can fix the leak in the seam of our large (8'W x 4'H x 2"D) acrylic salt water tank.
<<Eeek!!  A difficult challenge at the least!>>
The owner has said that he sign a waiver that relieves the repair person of responsibility if the repair does not hold.
<<While there are several ways that this can be repaired, no sane repair person will guarantee this work.  The best looking and safest repair will require emptying the tank, cleaning out the defect and filling the void with a two part polymerizing adhesive.  A cheap and aesthetically non-pleasing repair could be made by gluing an acrylic splint inside the defect with two-part or solvent adhesive after cleaning the area with sandpaper. >>
The leak is small and is coming from the front left seam, about half way up the tank.  The tank currently is filled to below this level and still has fish in it.  Can you recommend anyone that could take this sort of job on?  Regards,  Jennifer Ferguson,  Woodwork Creations
<<I don't know of anyone to recommend.  Beware that any repair does not address why this occurred in the first place... was the tank properly built to begin with?  Is catastrophic failure imminent?  Was the stand out of level?  Personally, I would strongly consider replacing the tank with one built by a reputable builder.  Best Regards.  AdamC.>>

Leaking Acrylic Sump...Silicone Not the Answer - 12/12/06
Hi and thank you all for your support and knowledge.
<<Hello...is our privilege to share>>
I have had my reef tank for over a year now with good success.  I am attempting to build a custom-size sump inside the stand of my 125 gallon running reef.  I purchased the 3/8" acrylic and had it cut to size so the fit seems to be good.  I used Weldon-3 in all of the seams.  I then let it dry and used Weldon-16 to form a bead around the seams.
<<Hmm, shouldn't be necessary if the pieces are bonded correctly with the Weldon-3, but won't hurt either.  If you really want to "strengthen" the corners/seams, you could cement in triangular shaped corner braces (these are offered/can be found "pre-made" on the Net)>>
I filled the sump with ½-inch of water and the water leaks out of the seams.
<<Mmm, perhaps the "fit" was not as good as you perceived.  For the Weldon-3 to work properly the joints must fit precisely to allow the cement to be drawn-in by capillary action>>
I tried to put another heavy coat of Weld-on-16 and let it dry overnight.  This also leaked.
<<Hmm...just spreading it over the surface isn't likely to help as you've discovered, but if you can "force" this thicker bodied cement in to the joints you might be able to fill the gaps/leaks.  If the leaks are many/large you will probably have to either cut the pieces apart and recondition the mating surfaces...or have new acrylic cut/prepped and start over>>
The acrylic shop said I should use 100 percent silicone to fix the leaks because it stretches.
<<A poor suggestion/option in my opinion...the silicone will not adhere well to the acrylic and though this may seem to work at first the silicon will eventually fail and leak...probably when you happen to be away for an extended period>>
I read on your website that silicon is not the best answer.
<<Correct>>
Do you think this will work only for sealing the water and not for the structure of the sump?
<<A poor solution for the former and disastrous for the latter>>
I also noticed the Weldon-16 does evaporate so the seal does become much thinner when dry.
<<Yes, the cement shrinks as it cures>>
Thank you.
Darrell
<<I would try the thicker cement again, using a finger run along the joint to force it in (do make sure everything is "completely dry").  If you aren't able to seal the gaps this way then your best/safest option in my opinion is to remove this sump and rebuild/start anew.  Regards, EricR>> <If this fails, RMF suggests securing a length of doweling (acrylic) cut to fit in the corners (I'd do all inside seams while you're at it)... With the Weld-On... Make sure and examine the doweling closely... it is often convex on two sides... you want the two flat sides against the current acrylic panels.>

Acrylics, leaks and silicone? 1/17/07
Hello<,> I have  a question.
<<Hello! We got answers!>>
I have a<n> older large acrylic fish tank<.> <I>t  has several leaks on the bottom where the seam is<.>
<<Yeeow! Talk about a bummer. Older, meaning "out of warranty"? >>
I tried to silicone the outside but it made the leak worst <worse.>
<<Two things. One: You don't ever seal leaks from the outside. It just doesn't work that way. Two: Acrylic needs to be welded to make a seal, using solvents, not goops. A popular method of bolstering every seam in your acrylic tank is to use acrylic dowels (square) and bond them to every seam. This procedure and more available at: http://www.wetwebmedia.com/acrylictkrepfaqs.htm >>
<H>ow does <do> I fix this<?> <T>hanks. William.
<<You got it, W.
-Graham T>>>

Cracked Tank
Hi there Bob I just cracked the bottom of my 180 gallon acrylic tank. Its okay it was empty. The crack maybe about 10"long. I would like to repair this problem if possible. Someone had mentioned to use "Weld On (I forgot the number) and attach a new piece of plexi-glass to the bottom, he also said that even if I glued the new piece on to the bottom the crack may continue to grow until it reaches the edge.
<Yes... I'd plan on this... you can likely make a good repair by solventing (actually the process here... not gluing) another thinner sheet of acrylic onto the bottom of the existing one... over the crack and all else.>
To remedy this problem I thought about drilling a small hole at the two ends of the crack to stop the crack from growing. Do you think this is a good idea? or do you have any other suggestions?
I look forward to your input,
<Do ask the folks at acrylic fabricating shops in your area, over the Net what they would do as well. I would solvent a piece onto the bottom and router off the edges. Bob Fenner>
James

Cracked acrylic tank
Do you see anyway of repairing this type of thing?  Could I drain the tank down and try some sort of glue?  Is there anything I could try before giving this thing up completely?  
<Sorry to hear of this major problem. I would contact an acrylic manufacturer about repairing this tank although I hold little hope for repair. You would be safer just getting a new tank. At the very least I would empty this tank ASAP and follow the suggestions from the last email. You don't want to put this off until the whole tank spills on the floor>
Thanks for your patience with me.  :)
<No problem...That's what we're here for! David Dowless>

Acrylic tank-?
I have built a corner tank with bent corners( had a fab company bend) which cost a pretty penny. I tested it out and there was a very small leak so I went back and applied more solvent and tested again, no leaks. I have had water in it for about 3 weeks just to see if there would be leaks after a period of time and there were none. In some of the seams though there is some air bubbles I have tried to fill them in with solvent but it does not seep into the bubbles leading me to believe that the edges are sealed. Do you think that these bubbles could present problems in the future or what do you think?
<Likely not a problem if it hasn't been so to date. Bob Fenner>
Thanks for the info,
                     James Wesley

Acrylic tank leak
Hello.  I recently purchased a used 125 acrylic tank and it has a leak.  
There is a crack on the bottom right near the front of the tank.  It does go all the way through the tank and that is where the leak is.  I was wondering if I could glue another piece of acrylic or Plexiglas along the bottom of the tank (inside) all along the front edge.  If that will work, what would you use to glue it?  Should I use crazy glue and activator on the crack first?  Please help!!!
<You can solvent (not really a glue... as there is nothing left between the melded materials) a piece of acrylic here (look for "square doweling" at an acrylic outlet (it's only truly flush on two of the four sides, and you want to fit these two against the existing panels). Look for Weld-on products for solvent. Bob Fenner>
Thank you,
Ron

Tru Vu (acrylic tank re) Repair
Howdy,
<Hi there>
I am very glad I located your site and appreciate the valuable information you offer.  I am in the process of repairing a 55 GAL Tru Vu acrylic aquarium which has some minor leaks.  
<Very unusual... I sold these tanks for several years... none were defective, or became so>
I am concerned because I used the traditional method for a glass aquarium and the tank is acrylic.  Last night I applied DAP 100% Silicone Aquarium Sealant to the length of the interior joints.
<Oops>
Do you happen to know if Aquarium Sealant is going to work or if I need to get out a razor blade and start all over with the Weld-On product you mention in  your postings???
<You do need to cut out the silicone and use the solvent. Bob Fenner>
Please advise.
Sincerely,
Dan May

Help!! Tank blow out!
Bob
I have a tank that is 45 13/16 inches wide by 94 1/2 inches long by 33  7/8 inches tall
One of the long sides blew out due someone putting their full  body weight on the top while retrieving a fish. It first just popped the seam by a couple of inches and this guy said he new how to  repair acrylic tanks. But as you can imagine he has disappeared. Now I have  no one who can repair my tank.
Desperately seeking an acrylic tank repair person  in Downey, California.
Sincerely,  
JC Benavides
<The tank can be repaired... should be drained, dried, and a square dowel inserted in the (I would do the whole inside edges) inside corners... take care to look carefully at and MARK the outside edges of the doweling that are curved (IMPORTANT: Note that only two of the four dowel edges are flush, the other two are concave...) and all solvented into place. Bob Fenner>

Tru-vu built-in overflow question
I just got a used Tru-vu 100 gallon long (60x18x20) tank with 2 overflow on each corner.
Question is internal overflow size is about 6x6 do you know how much gph is rated? I could not find this info from Tru-vu website...
<What is the diameter of the through-puts? You might call them as well>  
I was thinking about using 1140gph external pump on this tank but maybe this overflow draw more water than 600gph...
<? What?>
Also due to moving this tank (forgot to take off bulkhead during move) on both side near overflow area I have crack (not near by edge but near by internal overflow L shape area) which is about 2 inch (Both overflow area affected)
<Bunk! Happens all the time.>
I put 1/2" tick (5x2 and 3x2)acrylic outside of overflow L shape and inside overflow square shape acrylic (2x2) and glue them with tape plastic's glue do you think this will be enough?....
<Should be... I hope you're referring to having solvented pieces over the cracked areas and holes and re-drilling them>
once I have about 100lbs liverock 100lbs live sand and water... I am getting worried...
<I would fill and test it... outdoors>
Maybe I should send you some pictures...
Thanks
Chris
<Bob Fenner>

Help!  Acrylic Tank Leaking  07/02/05
Hello All! <Hello Tammy>
Have been rabidly searching your site (lots of great information here) for about 45 minutes.   I've found a few suggestions to the problem I'm having, but was still a bit fuzzy on the execution.  (one recommended using dowels)
The short short version is this:   I have a 110 gallon acrylic tank.  
Used for Saltwater.  It is only about 4 years old.   I bought it new.   
It has only been moved once since setup - I emptied it entirely and had it moved by pro's.     It has been in this apartment for 18 months without incident.   Tonight I decided it was time for the water change and drained off about 30 gallons.   The front has always tended to bow - but I was assured by the folks at the store that this was Ok.  I suspect something about the weight change made a seam leak - because all of the sudden I had a steady drip-drip-drip in 4 places under my tank.   (anywhere the stand was drilled or even seamed it leaked through)   And before I got the wild idea to try and improve the water quality - there was no leak.  (I'd been under the tank changing the filter pad and carbon in the sump first - so I'm certain of the "no leak" report).   So Yikes!   So after deciding that all future tank work should be done during normal business hours, I flipped over some Rubbermaid bins, wiped them out - and started transferring water from the tank and the fish.   I now have an upside-down playpen over the bin safeguarding the fish from my three inquisitive cats and 3lb dog.    
I've got the air and heater running in their bin, so I think they're Ok for now - though certainly not liking the close quarters.
Where should I start?  Are acrylic tanks typically warranted?    Do you expect I'll get anything other than a "good luck" if I phone the store?   I know I'll need to scrub out the tank now - anything that you would recommend to make sure that it's completely clean for repair?  
Usually I just use my scrubby on a stick and lots of elbow grease...   but since I have the chance to take it down and really go to town on it now - didn't know if you'd recommend something.    Once I've got it clean - Where do I begin to look for help locally?  I believe the leak is in the bottom seams because I got down to less than 5 inches of water and still kept dripping.   Is there something I can do myself?  I really hadn't budgeted for a tank replacement - and I'm afraid this is my first leak.   The fact that I'm on the 3rd floor and got thru the whole incident without leaking onto the folks downstairs has me reasonably confident that I could follow DIY instructions should you have any for me....  :)   Also - I'm a little worried that the leaking could damage the structural integrity of the stand...  Is that being over-cautious?  Or do I have more problems?   My father will come over tomorrow and help me lift the tank down for cleaning and I'll get a better view.   Maybe could put the hairdryer on anything still damp?
Thank you SO Much in advance for your help!   And Happy 4th of July!
Tammy <Tammy, you need to start at the store where you bought it.  Most tanks have at least a five year warranty.  At the same time, email the tank manufacturer about the leak problem.  Most will repair or even send a new one upon receipt of the defective tank.  James (Salty Dog)><<RMF would actually start by filling the tank up outside... with newspaper under it, trying to see if it is actually the tank itself leaking... very likely it his a hang-on device instead.>>

Re: Help!  Acrylic Tank Leaking
Hi Salty! <Hello Redhead>
Yeah, well you would think they would stand behind the goods, but the store where I  bought the tank has changed hands - and the new owner indicated that he thinks that the guy that they bought it from was hiring local acrylic shops to build tanks - as opposed to selling tanks from national manufacturers.   The guy was a little dodgy as far as when I would mention looking for my warrantee paperwork, he would just say that he was sure whomever made the tank was certainly out of business.   (which I loosely translated into - I'm not honoring a warrantee?)   Then the guy sat and wanted to sell me a new tank, new stand, and then he tried to flirt.   No game either.  Don't get me started.   I considered telling him that I was flattered, but that I was in a relationship and that my boyfriend was an attorney - loosely translated, You'd better honor my warrantee or I'll sue cause I have free legal.   LOL!  <I'm thinking when a store is sold the new owner isn't responsible to honor any warranties, especially since he didn't make any money on it.>   But I really didn't want to continue the conversation.   Just awful.   Instead of staying on point about my tank, kept talking about what a pretty redhead I am - (my hair is DARK Brown)   Doh!  Lousy service and just no game.  :)  Ugh.
My tank is a 110 gallon - measures 48 inches long, and 18 inches wide front to back, and 30 inches tall.   It doesn't look like Tenecor makes a standard tank with those dimensions.   Oh!  And Thanks for the tip on the self drill -vs.- ordered drilled.  Important Safety Tip.
Now if eBay is a marker of what's out there - the folks making tanks like mine brag that they're using the 1/2 inch - not that crap 3/8 that a lot of people try to get by with.   (dunno if that's true - that people use the 3/8, that is)
Tenecor does show a 140 tall:
This model features bent (seamless) front corners. Includes a clear acrylic top with filter slots, access hole(s) and matching lid(s). Dimensions are 60"L x 18"W x 30"H
Price: $913.00
While I can't find any documentation on their site as to the thickness of the acrylic, I did find a posting on another site talking about the thickness of acrylic to be used...  I've included the post content below, but the gent says that his company uses 1/2 inch thick acrylic for tanks up to 30 inches tall and 600 gallons.  He also mentions recommended/Ok "bow" measurements.  What to expect with glass and acrylic.   Dunno if it's correct - but thought I'd pass it along as well in case your interested.
Tomorrow I plan on calling my LFS that I trust - and then calling their suggestion for an acrylic shop.   I'll pass along the prices and info
that I get in case it's ever of any use to you or yours.   :) <If you don't live in a big town it may be difficult to find an acrylic shop willing to build an aquarium and guarantee it for a reasonable amount of time.  Keep in mind if you are or will be keeping corals, the deeper the tank the more wattage you are going to require.  James (Salty Dog)>
Thanks again & Happy 4th!
Tammy

(Damaged) Acrylic tank assessment 7/4/05
I am sorry this is such a long post.  I just don't know what exactly is pertinent information, so when you know enough just stop reading.  Reading the posts made me think really hard, and try to be perhaps too observant.  I posted here because you seemed to know a lot about tank integrity.
<Okay>
I brought home a free acrylic (I think, are there other plastics for tanks?)
<Mmm, really only very small ones... acrylic/s have many names, are about all of the same composition>
tank today.  It is a TruVu brand, 16 deep 18 wide 60 long.  There are cracks in the top and I don't know the owner (neighbor of an ex-boyfreind), so I can't get the history of the tank.
It looks like it belonged to a fraternity (stickers and spray-paint and graffiti).  My ex- did say he was told it doesn't leak.
<Actual cracks or just crazing? Can you feel breaks in the material? These are indicative of cracking>
I am afraid it will fail. I am not concerned about a slow failure, I am afraid that some of the cracks will just split with no warning after the tank is in use some time.  I also see what I think is some crazing.
<Ah, I see>
I haven't filled the tank to test it because I wonder if I should repair it first.  The link to the repair story is broken, so I couldn't read it.
<Unfortunately there is no such piece... just haven't gotten around to writing it...>
  If there is a quick easy fix that may hold this tank together, I will do that first.
<It may be that the cracks can just be ignored (fill this tank outside and see how it does), otherwise, the solvent used to weld the tank panels together may be used to anneal the cracked portions (call, write TruVu re Weld-On...). At worst, another panel (thin) of the same size, cut-outs may be solvented to the top/cracked one>
CRACKS:
These may have been produced by heat, as I read in other posts.  My reasons for thinking so are that the top of the tank is warped, and there is a small area of the top that looks like it may be air bubbles.
Does acrylic "Boil" from heat?  Also, the edges of the cracks are warped and do not match each other.
<Warping is common... these tanks bend quite a bit with use/time... boiling is very bad>
If the cracks were caused by heat, might the tank be compromised to the point that it will fail, because the top is an important structural member?
<Doubtful, but a possibility>
My reasons for thinking it is not heat is  I do not see any blackening or discoloration.  Also, one crack actually extends down the side of the tank about an inch.  Could this crack be from an impact?
<Yes, most likely... am starting to have glimpses of "Animal House">
I haven't filled the tank to test it because I wonder if I should repair it first.  The link to the repair story is broken, so I couldn't read it.  If there is a quick easy fix that may hold this tank together, I will do that first.
There are four cracks in the top of the aquarium, they all run from a corner of the large cut out to the side of the aquarium.
<These are best repaired per above>
The two in the back run from the side cutout to the 1-1/4 diameter hole, to the back of the tank.  One CONTINUES down the side of the tank about an inch, this portion of the crack is not perpendicular, but actually at an oblique angle to the tanks surface.   
<Also best repaired>
The tank top has two rectangular cut-outs, two smaller rectangular cutouts, six 1/4"D circular holes, and 2 circular holes about 1-1/4 "D.  One of the 1-1/4 inch holes is not really circular, it looks as if a smaller hole was drilled off center of the larger one, however the edges are nice and smooth, so I don't know if these holes were homemade, or poor quality control of the manufacturer.  But the crack is not located near this bump.
CRAZING:
It is a really sunny day and I noticed when looking obliquely at the tank outside that there was a glittery sheen inside the acrylic.  It seemed to be pretty uniform throughout the back surface of the aquarium, and I did not see any direction to it, just little spots of glitter.  I could not see them on the other sides of the aquarium, but this could be because I did not turn the tank to the same angle.  I suspect that it is crazing.  (If not, what could it be?)
<Likely crazing... though could be marks from solvent, local pressure or heat stress>
  I cannot see it at all when the aquarium is viewed straight on.  And I don't think I could see it in indoor lighting.  Is a certain amount of crazing a normal occurrence?  Does it happen in every tank?
<Is common>
USE:
When I first saw the tank, I thought that it wasn't very useful for a display tank.  Now I am thinking that it actually would look pretty funky as a type of urban  community tank.  What do you think of this idea?
Thank you,
Mary
<If you have the time, interest, worth trying to effect a repair. Bob Fenner>

Re: Acrylic tank assessment 7/6/05
Thank you for your reply.  I was unsure about how to weld the cracks closed.  The edges don't line up, and in some cases, the irregularities of the edges get in the way of realigning the acrylic.
I took the tank into TAP plastics today.  They suggested that I drill a small hole at the end of the crack before I weld.  This will relieve any stress at that point from the misalignment.
<Interesting>
This makes sense. (Lucky that all the cracks end one inch from the top.)
It is consistent with the reason that larger diameter corners are stronger, the stress is distributed over a larger area.  
<Yes>
The weld-on #16 cost $3.05.  The piece of scrap would have been $1, but he threw it in for free.  Must have felt sorry for me, trying to save such a pitiful tank.
He should only see my car! LOL!
<Likely>
He thought  the warp on the cross member would not affect its strength, and that I don't need to reinforce it.
<Okay>
He had no idea about the crazing unless it was a solvent.  I suppose its possible the gut tried cleaning it with something weird.  But I really don't think so, it is so evenly distributed.  
<Is just "stress" over time mainly>
I just wanted to share with you the idea of drilling.
  Wow a 75 gallon tank for $3.05!   I'll let you know how things go with my experiment.
<I'd appreciate this>
I will drill the holes, wash the tank (soap and water he said)
<Mmm, no... avoid soaps, detergents... toxic to aquatic life, hard to remove, leave a film... water and vinegar, possibly straight vinegar (white) for "scale"...>
and weld a piece of scrap over each crack.  I am toying with the idea of welding an acrylic divider in the middle to compartmentalize it into two tanks, but I haven't decided yet.
<Mmm, worth considering... but hard to change later>
I would prefer a removable divider, but since the acrylic will flex, I don't know how I could do this.
<There are commercially made dividers, but these are a bit flimsy for this sort of tank>
Right now I really could use smaller tanks.
Well its time to stop blathering, and see if this idea will hold water!
Mary
<Real good. Bob Fenner>