Buffing An Acrylic Tank – 08/26/09
Hello,
<<Hi Michele>>
I have purchased a used 300 gal acrylic tank and while removing the old paint from the canopy some of the stripper used to remove the paint dripped on to the side of the tank.
<<Mmm…left some nasty marks no doubt>>
Now there are two lines where the chemical ran down the tank.
<<Indeed… It really doesn’t take much to mark up an acrylic tank>>
What would you recommend using to remove these lines?
<<There are various methods and products about. One of the best solutions is the product line from Novus. These are liquid polishes in various “grits” that you use in succession and can remove anything from heavy scratches and abrasions to light haze. Another good option is a product called Micro Mesh. This product is more like traditional sandpaper but comes in very small grit/mesh sizes for buffing out abrasions in acrylic/plastic. Try a keyword searches on the names and see which you think suits you best>>
Thank you,
Michele
<<Happy to share… EricR>>
RE: Buffing An Acrylic Tank - 08/27/09
Thank you for your help! I will definitely check these out.
Michele
<<Quite welcome... EricR>>

acrylic woes. Nah   5/10/09 Hey crew, <Mike> I have a Clear for Life 55g acrylic show tank that I've had set up for around 3 years now. I chose acrylic because it looks nice, I liked the rounded corners (at first...I don't like cleaning them though...), and they are supposedly bomb proof since they are less ridged and don't have the risk of failing at the silicone seams. <Ok> my biggest concern was scratches, crazing and cracking. Scratches and crazing? ok...herding cats, I'm over it, but cracking was still a huge concern, so the stand is on carpet (I have wood floors) to help level and absorb any imperfections in the floor, and the tank itself is placed on 1/4" Styrofoam sheet (as per just about everyone's suggestions) to help level the tank and so on. <Wow. Thoughtful> anyhow, I'm moving in a week and completely restarting my tank. its been broken down, livestock sold, etc, mostly I wanted to start something new besides the usual community reef (I don't now what yet). getting to the point, when sitting down to start some scratch repair, I noticed some crazing around the rounded corners of my tank towards the top. I'm my reading (on your site, on scratch repair) it said watch for parallel cracks, particularly around the bent corners as they might be of some concern. <Parallel AND interconnecting verticals may be...> I've attached pictures of each side, they run parallel to the floor, the right side seems to be worse than the left. Should these cracks be cause for panic? <Nope> fortunately as I said there is no water in the tank but I'm a little concerned to even think about refilling it since I read these cracks could mean impending doom. thanks Mike <Naught to worry about here Mike. These are akin to "stretch marks"... the material weakened during heat bending/fabrication... not a cause for feelings of dire doom. This tank will not fail. Bob Fenner>

Crazing in my new/used 180 gallon tank. 3/28/09 Hi, <Hello> I am pretty sure I have made a terrible mistake buying my first acrylic tank. <Oh?> I am in need of serious help. I purchased a used 180 gallon "Sea Clear Aquariums" fish tank. <Am very familiar with the company (and its subsidiaries, other businesses) and its products> After reading your wonderful site, I believe it is "crazing" in the front middle and around few edges/corners of the tank. <Mmm, the one pic looks like repetitive impacting (maybe from a hood?) the other appears to be crazing...> This tank is only 3/8" thick all around, which I now realized it is much, much too thin for a 6'x2'x2' tank! <Mmm, yes... and "is" thick "enough" for these dimensions... though, if it were me, I'd make these out of 1/2"... Do badly bow in the mid-back and front...> I was advised by an Expert that I can't fix the crazing but I can prevent it from getting worst.  I need to know from you if this is sound advise- I will need to reinforced the top panel of the tank (between the two openings) with three 3/4" or 1" thick pieces of clear cell cast acrylic. (2)6"x24" and (1)23"x24" using Weldon #16. <What? No... this won't help here> The materials for this reinforcement will be around $100. Will this work? <It will indeed! IF you can find, buy acrylic for this cheap, get all you can, sell it at market and buy yourself a new tank!> I spend a lot of money on this tank and do not want to spend more if I can fix it. <I would spend nothing on the present tank for a repair... it won't likely "fail"... catastrophically...> The tank is currently sitting empty in my garage. Please help! I have attached pictures. Thank you in advanced. Charlie <How to state this better for you? Many acrylic tanks have such imperfections... some getting worse quicker... Tanks et al. are fabricated of thinner materials to "keep costs down"... What you have is not atypical.  Bob Fenner>

Re: Crazing in my new/used 180 gallon tank 3/28/09 Thank you so much for the respond. I just want to clarify a few things... 1. Are you saying that by reinforcing the top panel with additional 3/4" thick acrylic will help prevent further "crazing"? This will help, not hurt the tank. <It will make no difference re the crazing.> 2. Will 1" thick be better? <No.> 3. Will the additional weight (from the new three pieces) on top of the tank "harm" the tank? <No.> 4. Is it your advice that I do not need to "fix" this problem, but if I want to (for my peace of mind), it will help the " longevity" of my tank? <No.> The cell cast acrylic I am buying is from Ebay. <I would not use this....there are some very inferior acrylics out there even though they are cast.> Thanks again! <Welcome, for what it is worth I would just use the tank as is...as Bob said it will bow quite a bit, that is the M.O. of this particular model tank. Save your money for a future tank! Scott V.>

Acrylic Seam Cracks/Crazing 7/3/08 Greetings, <Larry.> I enjoy reading WetWebMedia on a regular basis. Thank you very much for all the time you put into this site! <Ahh, thank you!> I have a Clarity Plus 240 gallon acrylic aquarium (8x2x2) that I recently purchased. The previous owner used it right up until I took ownership of it. They just moved to a new home and have a 300 gallon reef built into one wall. <Fortunate for them, and you!> The tank looks to be in perfect condition except for the seam where the top of the tank meets the front of the tank. All other seams are crystal clear and look absolutely perfect. There are tiny cracks in the seam itself. I have attached a photograph showing what it looks like where the cracks are the worst. <Appears to be normal acrylic crazing. This can form due to manufacturing, stress, heat, acrylic used and about a million other reasons. Not really of any concern so long as they do not extend past the seam.> I would say that there are no cracks along half of the seam, minor cracks for the other 30% of the seam and the type of cracks as seen in the photograph for the remaining 20% of the seam. How much should I worry about this joint? <No, just about every acrylic tank has this to some extent in time. Given the location and lack of crazing in other areas it was likely caused by weight from a canopy/lighting fixture.> I read on your site that someone was planning to gusset the inside of a seam with square acrylic rod and some Weld-On. The canopy for this tank overlaps the top of the tank by about 1-1/2" so I have some space to work with. Do you think that if I purchased some 1/2" or 3/4" square or triangular rod and used some Weld-On that would strengthen this seam substantially to take any worry away? <You certainly could do this if it makes you feel more secure, I honestly would not go to the trouble here.> What shape and size of rod and which type of Weld-On do you recommend? <A little will go a long way. Your tank is likely ½”, so if you were to use ¼” rod you have increased the seam-weld area by 50%. It will cost you little to nothing to pick up a piece of ¼” scrape from a local plastic fabricator, you can cut some strips. Weld-On 3 or 4 will work fine.> Thank you for your time! -Larry <Welcome, Scott V.>

Links  08/08/2005
Hi, I am a reefkeeper and regularly scan your site for answers to questions.  Very nice site, thank you.  We recently launched a company called Everclear Transparency Refurbishing Inc (aka ETR-INC) at www.etr-inc.com  We primarily sell acrylic scratch removal kits and products right now, but are quickly expanding our inventory to include other scratch removal accessories and maintenance products.  We also plan to add lots of useful information and tips to help reefkeepers avoid scratches.  Could you please post a link on your site for us?
<Will gladly do so>
At some point we may be interested in buying some ad space on your site but we're too poor right now.  Thanks again!
Regards,
Scott
Everclear Transparency Refurbishing Inc.
www.etr-inc.com <http://www.etr-inc.com/>
scott@etr-inc.com <mailto:scott@etr-inc.com>
<Bob Fenner>

More Myths About Livestock Scratching Acrylic Tanks - 11/18/05
I recently bought a 220gal Tenecor tank (72X24X24) with the Simplicity Plus system with the intention of setting up a FOWLR system. I originally wanted to buy a shark, but after reading your site, I realized that this tank is simply too small for one.
<<Yes, and shaped wrong too.>>
I would like to put a couple of triggers in though, maybe a Blue Throat and a Picasso.
<<Cool! I have a Blue Throat in my Tenecor 375.>>
The guy at my LFS said that triggers sometimes scrape their teeth along the sides of the tank, and since this is an acrylic tank, I thought I'd better check. I've never read about this behavior, have you?
<<Nope...probably falls in to the same category as the stories about the Ctenochaetus genus of tangs scratching acrylic tanks with their teeth...mostly wives tales. >>
<<Did you bring this up with your wife?  MH>>
I think you need not worry...and believe me when I say...YOU will put far more scratches in the tank than any fish!>>
Thanks!
Robert in Texas
<<Welcome, EricR in South Carolina>>>Mmm, do agree with the hobbyists causing more scratches... but have seen trigger-made scrapes in acrylic... and a Pleco-destroyed one recently. RMF<

What causes Acrylic crazing  - 01/23/2006
Hello
<Hi there>
    I have three questions that I hope you can answer.
1. What causes crazing in acrylic? Does it normally occur when the material is under tension or can it occur in raw sheets of acrylic also?
<Mmm, some acrylic seems to craze much easier than others (one could say this is a "quality difference" I suppose). And some does this without actual construction, use, with time... particularly if/when exposed to sunlight, heat... But most crazing does occur in actual practice, in areas of higher torsional stress... corners, near upper front seams...>
2. I have heard about a two part acrylic cement that some acrylic aquarium manufacturers use, they say it produces stronger bonds compared to standard the standard  one part" Weld on" cements.  Can you tell me what this two part stuff is?
<Nope, don't know re>
I've never heard of it. It sounds like a type of epoxy but I don't know why one would want to use epoxy to join acrylic.
<As far as I'm aware, Weld-On and similar solvents actually melt the acrylic together (not cement)... done "right" (square cuts, clean...) there is nothing stronger as far as I'm aware>
3. I'm planning a tank 120L X 24W x 30H using 1" cast acrylic for all surfaces. I'm trying to keep bowing to a bare minimum for a tank of this size, do you feel this height is safe for 1" thickness?
<Oh yes>
Have been reading your site for awhile and respect your suggestions, this site has been a great resource to many of us. Thanks again.
Sean
<Thank you for your kind words, acknowledgement. Bob Fenner>

Underwater Acrylic Scratch Repair - 06/29/06
Hello,
<<Hi!>>
I must have picked up a rock cleaning the acrylic and got several scratches on my boss's 90 gallon tank.
<<Is easy to do>>
I ordered the product above and would like your opinion on using it.
<<Is fine for small repairs>>
Can you really use this product under water with the fish in there?
<<You can.  The sanding action obviously will liberate fine acrylic particles in the tank, but these are not harmful to the tank inhabitants in my experience>>
Do you know if it works well?
<<That depends much upon you.  Follow the directions closely taking your time, and don't "skip" grades of  abrasive.  Also, be sure to "feather" the repair to reduce the risk of creating a "lensing" effect.  And if you find you need more/finer abrasive sheets you can get them here without buying another "kit": http://www.sisweb.com/micromesh/mmr_sheets.htm>>
I understand it's time consuming but that is no problem.
<<Indeed...not an easy task>>
Also we would like to buy a clownfish but we're wondering which would be the less aggressive?
<<Mmm, in my opinion Amphiprion percula is one of the more "gentle" clownfish species>>
Thanks for your help!
Nancy
<<Happy to assist, EricR>>

Acrylic Tank Scratch Repair - 06/07/06
Hello,
<<Hello>>
I found your site on Google and wonder if you can help.
<<I'll try>>
A friend of mine recently bought a used 300 gal. acrylic tank.
<<Neat!>>
The problem is it's scratched from head to toe.
<<Common>>
We said we would make it a project to restore it and have since bought a few of the Pentair restore kits, but this seems to be making the problem worse.  Spoke to a representative from the pet store who informed me that it is impossible to fix that size tank with the repair kits, it would take forever.
<<Indeed, these kits are meant for touch-up/spot repair>>
I have however seen where you recommend Novus.
<<A good product, yes>>
Is it similar to the scratch removal kits in that you have to sand the acrylic, or is it just a rub on formula?
<<Novus is a "liquid" with different grades of abrasives used in succession.  Best/quickest results come from using in conjunction with a power buffer (electric or air), but can also be used "by hand"...with much elbow grease>>
How many ounces would it take to complete a tank this size (8ft/3ft/2ft)?
<<Difficult to say, depends much on the degree of damage...but likely cheaper in the long run than the Pentair kits>>
Also, I don’t know if I am pressing too hard on the sandpaper, but I can't seem to get out all the lines I have made.  They are extremely fine but still visible at an angle, and hazy in some spots.
<<Are you using the paper "wet"?  Have you tried buffing with the liquid polish?  These kits are pretty good for small touch ups on a tank that is "in operation" as you can use the abrasive sheets under water.  But given the fact that your tank is "dry", I would proceed with the Novus product.  You might also try posting your questions/challenges in the DIY forum on Reef Central.  There are several acrylic tank manufacturers that frequently monitor the forums that could likely provide some useful tips>>
Your assistance would be greatly appreciated.
Much thanks,
Issaco Mignott
<<Good luck with your project, Eric Russell>>

Scratch-Proofing an Acrylic Tank...Not Practical Really - 01/21/07
I have a 90 gallon acrylic tank (marine) that I'm setting up which is starting out unscratched.  I am planning to fill it with a lot of live rock, which I'd like to allow to lean against the back, and side walls of the tank,
<<It's best to leave space between the rock and the tank walls for adequate water flow to preclude dead spot/buildup of detritus>>
so I'd like to put a thin layer of something inside the tank to protect the acrylic from being scratched by the LR.
<<Mmm...not very practical really>>
Ideally it would be black.
<<Then what why worry about it if you won't be viewing the tank through these panels?
Since I can't roll up a sheet of glass to fit it through the access holes in the top of the tank, I'll need to use something that is flexible enough to roll up and get inside.
<<Then you will have problems with the edges "curling" as gluing something in place will be difficult and will also "mar" the acrylic>>
What can best meet these criteria (and please add any criteria that I should also consider):
1) non-toxic
2) not very expensive (less than $20 for a 2 x 4 foot piece?)
3) looks nice in the tank (not a lot of seams)
<<Nothing that comes to my mind will fit these criteria for reasons I've already stated>>
How should I affix the material to the back wall?  If I use an adhesive, it must be removable later and not hurt the acrylic (or the fish).
<<Again, not practical...pretty much anything that would hold will mark/etch the acrylic>>
If I use silicone adhesive, will it discolor or damage the acrylic?
<<I have seen this cloud/discolor acrylic>>
Will it adhere well enough?
<<As I see it, your only options to black-out the tank back/sides is to either paint the outside surfaces or affix painted panels to the outside surfaces...neither of which will prevent scratches to the inside of course>>
If I just lean it in there, will I have problems with live stock or algae getting back there?
<<Likely so, yes.  Honestly mate, what you propose is just not practical in my opinion with the small openings limiting the use of "rigid" material and the adhesive "marking" issues.  I think you'll just have to bite-the-bullet and accept the fact the back/sides will get scratched.  As will the front, despite your best efforts...trust me I know [grin].  On a positive note, if you decide to sell or use this tank in a different configuration some day (e.g. viewed from two sides), the scratches can be removed and the tank polished to look like new...though not without a measure of "elbow grease">>
(I'm considering making this an octopus tank)
<<Be sure to read here (http://www.wetwebmedia.com/cephalop.htm) and here (http://www.wetwebmedia.com/cephsysfaqs.htm) as well as among the associated links in blue at the top of the page.  Regards, EricR>>

What eats acrylic?
Dear Bob,
A quick thank you for all you’ve done for us “salts” out there.
I reference WWM frequently and often and thank you and Lorenzo for all the time, effort, and sage advice you’ve devoted to people’s better understanding of the life forms and biotopes they keep.
<A pleasure and honor my friend>
I have a question regarding what I believe to be radula marks etched into the surface of an acrylic tank. I recently helped a friend break down his 40 gal. tank (SeaClear or TruVu, I’m not sure which). He had (sadly) neglected any maintenance on the system since his last specimen died some two years ago, only adding top off water. Needless to say it was a huge mess, but somewhat of an interesting study from a scientific perspective. As I began to scrape of the thick filamentous algae covering all sides of the tank, I noticed a haze on the front panel. Upon closer inspection, this haze was a pattern of etchings in the acrylic surface! The pattern matches that which I have seen snails (esp. turbo) leave as they graze through a patch of Cyano. Is it possible for snail’s radulas to be so hard as to etch into the acrylic? 
<Yes... for browsers, many gastropod mollusks have a rasping mechanism... a "tongue" called a radula (important in its characteristic make up for species identifications at times) that is constantly being regenerated in the back of the mouth, worked by a muscular device, the odontophore... that these various "snails" use to scrape away micro/macro algae et al. from hard surfaces as food... Some have modifications, additions of specialized salivas, bore into shells, melt rock...>
I am wondering if you have ever encountered this, and if so, what species of snails you have associated it with. I am sure this info would be quite interesting to everyone out there with an acrylic reef tank.
<I have seen this sort of marking... and simple "stress fracturing" that looks similar... in acrylic tanks. Don't know which specific species might be involved though. Bob Fenner>
Sincere Thanks,
Karl

Is acrylic scratch remover safe for fish?
Hello Mr. Fenner,
I just got finished putting my new tank together. I have the powerheads, the heater, and the aragonite sand and water in. I have not yet put it the salt. I'm just testing the components and letting the sand dust settle. While inspecting my tank, I noticed in the light that there seems to be a very slight haze in a couple upper corners of the tank. I believe it might be from the TruVu SRK (scratch remover kit). 
<This may be so... or typical "stress fracturing" marks from heat-bending in those areas>
I might of accidentally not rubbed off all of the scratch remover paste thingy. The water has a oil spill type look when viewed at a lower angle. Is this bad? Shall I take out the water and wash the tank again? Please help. Thank You.
<Ahh, our businesses (retail and service) used to sell many TruVu/Aquaplex tanks... and I've spent many hours with the green and tan pastes you mention in their scratch removal kit. This material is not toxic. I would not take the tank down, or worry. Bob Fenner>
Stan

Taking out scratches from the inside
Bob,
do you know of any acrylic scratch removal kit that works underwater?
<No... all require draining the system at least down to the level of the work. Bob Fenner> Thanks,
Lee

Re: Is acrylic scratch remover safe for fish?
Thank you very much. That is what some people suggested on ReefCentral, but to hear it from an expert like you makes me feel so much better. 
Thank
you again and have a Happy New Year.
Stan
<You as well my friend. Be chatting. Bob Fenner>

Crazed Acrylic/Tank Cleaning 4/12/07
Hi Crew,
<Hello Christine>
I was wondering if there was any way to fix crazed acrylic in an aquarium?  
Is it just buffering it out, or do you have to just replace the acrylic (which would be hard considering I'm talking about a seamless tank)? I'm asking because  I am considering buying a 100 gallon tank, but it is crazed in the center of it-  almost 1 ft across and almost the entire height. I have no knowledge how it  happened,
<May not be crazed, but scratched from cleaning with abrasive material.  Generally, this won't be quite as noticeable with water in the tank.  My advice would be to buffer the acrylic with an acrylic cleaning kit such as Lifeguard's.  This will remove scratches, but if it is crazing, it won't help much.  Drs. Foster & Smith sells this product for around $20.00.>
do you know any reasons why acrylic crazes?
<Generally from stress and/or cheap acrylic which is more brittle than quality acrylic geared for aquarium use.>
Thanks for your help, your website is terrific!
<You're very welcome.  James (Salty Dog)>
Christine

Scratches on Acrylic Tanks
Hi Bob,
<Good morning! Steven Pro in this morning.>
I have an old 125 gal. acrylic tank with scratches from rocks falling and coral pieces bumping into the tank.
<A common problem with this material.>
How do I remove the scratches?
<There are various products on the market for buffing/polishing the acrylic to like new status.>
The tank is empty now,
<Which makes this procedure much easier.>
and has been torn down for about a year. I would like to set it back up but I would like to try to make this tank look like new. Any information would be greatly appreciated. Thanks Kevin Shimabuku
<Check out any of the dry goods e-tailers for acrylic repair/polishing kits. -Steven Pro>

Scratches (acrylic repair)
Hi Bob,
I have a 300 gallon acrylic reef tank that has a few scratches in it. I ordered some MicroMesh scratch remover pads from an acrylics shop on the web that can be used to "polish" out the scratches without using any scratch remover compound.
Is it safe to use these polishing pads inside the tank to buff out the noticeable scratches in a small area ?
<Yes... but does require that you lower the water level below the area to be smoothed out. Bob Fenner>
Thanks,
Chuck Spyropulos

Acrylic
Do you know of any way to buff scratches out of an acrylic tank? Thanks! :)
<Yes... have spent a bunch of time trying to do so... slight liquefied abrasives, to papers to "heat burnishing". Please use the Google search tool on our sites homepage or indices (on WetWebMedia.com) with the terms "acrylic repair" or "scratch removal". Bob Fenner>
Elizabeth K. Birdwell

Acrylic Scratches
Bob-
<Scott F. here this afternoon>
I recently purchased a 65 Gallon acrylic tank. Not thinking I scrubbed the inside of the tank with a Scotch pad (green, abrasive cleaning pad).
<Made that mistake before, myself!>
I then installed my power compact lighting and turned it on and to my dismay I saw that I have tiny surface scratches all over the inside of the tank. Is there anything I can do to remove them? PLEASE HELP ME!
Thanks, Mike
<Well Mike- this has happened to just about everyone who's ever had an acrylic tank- so don't beat yourself up over it. There are "repair kits" available to remove surface scratches, but they do involve sanding with various grades of specialized sandpaper. The scratches can be removed, but the work is kind of tedious! Do consult the dealer where you purchased the aquarium for a source of these kits, then get to it! Good luck!>

Need help please (scratch, opacity from acrylic tank repair)
hi bob I bought a 60 TruVu tank and had a scratch in it my LFS gave me some srk-1 to remove it now I have a big smudge is there some thing you can suggest I can buy to polish that out thx for any info
<There are "finer" polishes (often scratch-removal kits come with more than one grade) to "polish around" such hazy areas... in a pinch, if the area is small, you can even use a gritty oral dentifrice (aka toothpaste) and a soft rag to buff out such blemishes. Bob Fenner>

Acrylic Nightmare
Hi,
<Hi there! Scott F. with you>
This is in response to a prior FAQ.  I have an empty 55 gallon acrylic tank that's in need of some serious scratch removal.  I wanted to know if the headaches in trying to do this myself is worth it.  I've seen a few of the various kits that are available, but I want to know if there's any one particular kit that is recommended over another.  If it's feasible, I'd like to get the tank professional restored but I don't have any clue where to
take it.  I live in the Orange County/Los Angeles area.  Please help! Thanks so much.--Chris Sartor
<Well, Chris- "worth it" or not is a relative term, I guess. Depending on the severity of the scratches, it may be almost impossible to get 'em all without days on end of work. I won't kid ya- it's a very tedious process, and if you're doing a lot of scratches, it can become a "lost cause" at some point. However, if you have the time, and don't mind the effort- you can certainly pick up a tank at a good price and get it quite a bit nicer than it is now. As far as having it professionally restored- this may be one of those things that make it not worth the $$$. If you can find someone who can do it, they may charge enough to make purchasing a new tank look attractive! I'd try contacting a manufacturer or two for possible referrals. In the LA area, I think you could call Advance Aqua Tanks (Clear For Life), and see if they have some ideas. Good luck! Regards, Scott F>

Scratching His Head Over A Scratched Tank!
Aloha WWM Crew,
<Howzit? Scott F. with you today>
Thanks for all your help.  The service you provide is second to none (no ka oi).
<Thanks for the props! Glad to hear that we've been helpful for you!>
I have written a few times about my 55gallon FOWLR. I'm thinking about purchasing a used 200 gallon acrylic tank, but I have some questions before I  jump into such a big investment.  First, the tank has many huge scratches on the inside as well as the outside of the tank.  The current owner has many kids that destroyed the outside of the tank.
<Those darned kids... :)>
There are so many scratches that you can barely see into the tank.  The tank is a SeaClear and seems to be in good condition
minus the scratches.
<An all too common problem with used acrylic tanks! But also a common reason why used acrylic tanks can sometimes be had for cheap prices!>
I was wondering if the tank would be worth the headaches of trying to remove all the scratches.  Are there any other issues I need to be aware of?  Could the scratches lead to a leak or cause the tank to crack?  
<Well, Jeff- if they are basically surface scratches, they can actually be removed with a special sandpaper kit made especially for this purpose. It is a rather tedious process, unfortunately...but it does work! As long as the scratches are not "deep", or near the seams, then the tank is probably structurally sound...Do check on the condition of the chemical "welds" on the corners of the tank, to make sure there are no signs of them pulling away from each other. As long as the tank is structurally sounds, and as long as you're up to the challenge of sanding away the scratches (and if the price is damn good!), you may be able to score a killer deal on a tank that you can get lots of usage out of. Do check our sponsors for these acrylic refurbishing kits. There are other places on the net that offer these special grades of sandpaper. It's worth a shot.>
Mahalo Nui Loa-Thank you very much, Jeff
<Malama Pono and Ahu'i Hou! Regards, Scott F>

Acrylic tank cracks? (crazing)
>Hi all at WetWebMedia,
>>The crew says hello, Marina at your service.
>First I must confess your website has been a great help to me for the past year in looking up what to do when in doubt with my current trigger FOWLR set up.
>>What a confession.  Now, what penance...10 lashings with a wet noodle, then eat the noodle.
>Now, on to the point...
>>Oh yes, there was a point.  Having too much fun, back to work!
>I have recently purchased a used acrylic tank 76 1/2 x 15 x 30 (made by a local company).  The tank has an overflow to the left side and that is why it is longer than 72 inches. Total volume
is 150 gallons. Now, the previous owner had attached a piece of plywood or strip of wood across the upper edge of the tank to support a DIY canopy. While I was cleaning the tank I removed
the wooden strip which was attached with adhesive tape. Immediately I noticed a series of parallel marks that looked like cracks on the outside of the tank. There are 3 clusters of
less than an inch marks/cracks on the upper side (roughly half an inch before the brace starts). I'm not sure whether I caused that my pulling the wooden piece , or whether it was there from before and the previous owner had attempted to conceal it.
>>Bingo, I think it was there and he wanted to conceal it.
>Also, the same marks appear on the back side of the tank along the upper side but they are not as long. This leads me to
believe that I did not cause the damage (if it is to be perceived as damage).  Do you think if filled with water, it will cause a leak down the road?
>>Very well could be a problem.  I have a recipe for filling such "tight" cracks (please, please, let's keep it clean here), but have never used it on a tank that is so peppered with these cracks.
>Should I make arrangements to have it repaired, or sell the tank? This will be a FOWLR tank with 1 niger, black patch, blue line
triggers. Currently, all are at 3-4 inches long.  I would greatly appreciate an opinion on this...keep up the good work on WetWebMedia.
>>Well, if there is someone who can make good repairs and they can price them out for you, allowing that the repairs are not going to end up costing you the price of a new tank then I don't see why not go that route.  I would first fill the tank in my yard, on a flat area, to determine several things.  First: is it going to leak?  Second: are the cracks just so unsightly that I don't want this as a display tank.  Third: are the repairs proposed (my recipe will only stop leaks, you'll still be able to see the cracks quite well) cost effective.  At this point, only you can determine these things, then go on from there.
>>My recipe for repairing these cracks is that you must first ensure that they are completely free of any and all debris, including any mineral/salt deposits.  Once the cracks are to a pristine state, you need on hand liquid cyanoacrylate (Superglue) and the catalyst used for acrylic nails, and a small metal stick (like the tool used to push back cuticles...hey, I'm a lady!).  What you want to achieve is to get the Superglue to seep into and fill the cracks completely, then IMMEDIATELY place a drop or three of the catalyst onto it.  These substances react with each other (the hotter and drier the weather, the more immediate and extreme the reaction) to fuse with the each other and the acrylic to form a tight bond.  However, as I said, you will still be able to see the cracks--this is a method I've used on non-display tanks only.
>>Good luck!  Marina
Location of marks
_____________________________________________________
| """" """ "" | Hope
this helps to visualize
| | what
I wrote above.
| |
| |
| |
| |
| |
_______________________________________________________   <-- front panel.

Front panel 1/2 inch thick. Bottom panel is 1 inch thick.

Acrylic tank cracks?
>Thanks for replying Marina,
>>My pleasure, Dimitris.
Well, I called the LFS that sold the tank to the person that I bought it from and the local guru there said that if those clusters of lines are not close to the seams or corners, I shouldn't worry about it. He said I might want to buff it with a 3500 rpm electric drill, but he thinks due to the thickness
of the front acrylic panel( 1/2 inch) that it should be ok.
Personally, I could not see any of those surface lines |||| |||| |||| extend past the surface. They had no depth, just like those spider web like ones on the back panel. I guess I will fill the tank up with water to see if it will leak.
>>By your description, it sounds as though the only problems you'll have will be cosmetic.  C'est la vies!  Marina

Tough acrylic cleaning question
I have purchased an acrylic tank from a friend. He had applied some clear shipping tape to the openings in the lid. I have tried elbow grease and my credit card but the stuff just isn't coming off very well. I've looked around on your site and didn't find anything appropriate to my situation. I know not to use Windex or anything else ammonia based. I've thought about goof off but that's petroleum based. Do you have any ideas.
Thanks
<I would try "citrus based cleaners" here first. Do with the tank empty and make sure and wash any residue from the surface. Bob Fenner>

Re: tuff acrylic cleaning question, repair
Thanks Bob,
I ended up having to use lighter fluid to clean this stuff off, it was caked on pretty good.
<As long as you're "right there" wiping off the excess (so it doesn't melt the acrylic) this works pretty well>
I have another question. I found two small chips on the corner of the bottom plate, about 1/4" around and maybe 1/8" deep. The acrylic is 1 inch think at that location so I don't think it will be harmful. Do you think that I can put some acrylic glue in the chip just to give it some strength in that area.
<Might help. Have you considered adding some "square doweling" in the corner. This stuff comes in stock sizes with two of the four sides "square" and the other two a bit concave. You solvent (as in with Weld-on) the two flat sides to the tank inside corners. Bob Fenner>
Thanks

Scratch removal and polish on inside of tank using Novus products
Great site for info!
I have a Tenecor 180 gallon acrylic tank that has numerous fine to moderate scratches in the upper half of the tank as a result of five large red hooks bouncing off the front panel when it tries to compete for food against a 20 inch jardinei.
<Neat>
I am removing the red hooks and want to remove the unsightly scratches inside the tank.  Tenecor sells a group of products called Novus #1, 2, and 3 that is supposed to remove these scratches, as well as a micro mesh kit that does the same.
<I have used these products. They work... but the micro mesh reminds me of the Karate Kid series of movies... rub on, rub on... and takes about as long to remove the finer scratches it makes as re-watching the whole series!>
In doing the scratch removal, I would prefer to use the Novus products  The micro mesh kit seems very tedious and I do not feel comfortable with the acrylic particles being sanded off and mixed in with the water and substrate.
<Me neither>
But is it safe (non-toxic) to use Novus on the inside of the tank after the water is taken out of the tank to the level of the lowest scratch; or am I stuck using the micro mesh sandpaper?
<I'd try the two grits of the Novus first>
  If I can use the Novus product inside the tank, is there additional prep needed after the scratches are removed and the front panel is polished, before I can refill the tank?
<No further prep... just wipe up the bits of "scum" with a damp paper towel>
Thanks for the help!
Steve
<Thank you for writing, good luck. Bob Fenner>

Re: follow-up on removing scratches in acrylic tank using Novus, and visit to Phoenix
Thanks, Bob, for your very prompt response!
It is comforting to know that your experience shows Novus 1, 2, and 3 can be used on the inside of an acrylic tank without harm to the fish. I bought the Novus 1, 2, and 3 yesterday afternoon.
<Wish I had made these products!>
As a follow-up to my earlier email to you, can I leave my large jardinei in the tank while I am working on removing scratches with Novus 2, and if necessary, Novus 3. That is, from a chemically (nontoxic) safe standpoint?  
<As far as I'm aware, yes. Have used these in "full tanks", fresh and marine, with impunity>
There will be about 4 inches of water for him to stay wet;
<And not jumping out!>
the lowest scratch to be removed is an inch above this water line.
Thanks in advance for your advice!
BTW, Phoenix has a dry heat this time of year ... and its been mild this week. Its the August monsoon that you want to avoid.
Steve
<Will be out there this Thursday with some friends/associates, giving a pitch at the DMS (Desert Marine Aquarium Society). Stop by if you'd like. Bob Fenner>

Acrylic Tank Scratches
Hello all:
<Hi there>
Just a real quick question so I don't botch things up. We have a 125G acrylic that has developed some scratches on the front panel. I must have failed to notice a tiny bit of gravel in the pad while cleaning, as I am vigilant about making sure that no debris is in the pad before I use it on the panes.
<Good idea>
Nonetheless, I went on the website and found Bob's response to a similar query, where he recommended using a gritty toothpaste to remove minor scratches. I was wondering if this procedure can be done while the scratches are under water. I can apply the toothpaste without any difficulty, as the scratches are within arm's reach. However,  I am very concerned about the effects, if any, that the dissolved toothpaste may have on my fish.
Thanks for the clarification.
Mitch
<Mmm, they may end up with "whiter, brighter teeth" and a "significant reduction in dental caries", but should otherwise be fine. Bob Fenner>

Re: Acrylic Tank Scratches
Thanks, Bob...I am sure that my porcupine puffer, with his sizeable bite, will appreciate the brushing! I will try and get a paste that is recommended "by 4 out of 5 members of the American (Fish) Dental Association."
Mitch
<Ha haha, heehee! Be chatting. Bob F>

Acrylic Scratches
A few months back you mentioned a way to remove scratches from acrylic aquariums even under water.  Due to travel requirements I was out of town for the next few days and missed it if you elaborated on the subject.  I have checked the web site I was directed to by Bob but still haven't found any specific
instructions.  Can you please help me out?  Thanks
<Alright, I hope you can find this one! Most scratches can be polished out, depending on depth....  There are kits available from most on-line suppliers carrying acrylic tanks that use abrasives in finer and finer grades to remove the scratches and restore a lustrous finish, even under water with some. You might start by searching for these products at some of our sponsors!  Thanks for your patience.....Craig>

Invertebrates that scratch acrylic tanks 5/11/03
Hi can anyone tell me which invertebrates can scratch my new acrylic tank?   And which ones won't do any damage to the tank? Thanks, Ron
<mostly limited to mollusks with a radula (hard rasping tongue-like aspect- Gastropods predominate.)... and some echinoderms. Generally not a big deal. Best regards, Anthony

- Scratches in the Acrylic -
I have an acrylic TruVu aquarium and it is scratched on the outside and looks hazy in some parts.  What can I do or use to take these scratches out? Yoquin
<There are several commercial 'acrylic scratch-repair' kits out there. Look on the online retailers and you will find them. Cheers, J -- >

Coralline Algae and Acrylic Aquariums 1/14/03
Hi Bob or Crewmate,
<Hi Joseph. Adam here tonight.>
I haven't even received my custom acrylic tank and I'm already fretting over scratches.  Bob, in his book The Conscientious Aquarist recommended acrylic tanks over glass.  I just started reading The Reef Aquarium and Delbeek and Sprung suggest that acrylic tanks are more suitable for fish only because cleaning the coralline algae off the walls will scratch the acrylic due to the calcium.
<A question for the ages!  Some folks swear by acrylic, some swear at it!  Acrylic is a better insulator, is clearer, is lighter and is more shatter resistant, but scratching can be an issue.>
Just how much of a problem are scratches with an acrylic tank?  If I am careful and use the proper tools to clean the tank, will I be able to enjoy watching a marine environment in my home for many years without seeing obvious scratches on the acrylic panes?  Even though I am willing to invest substantial time, energy and money in setting up and maintaining a reef aquarium, I am not willing to do this if, after a few years, I am seeing a scratched viewing panel first and a reef second.  I would just as soon fill the 145 gallon tank up with freshwater and goldfish.  Thank You,  Joseph Rouse
<There are a few tips for keeping acrylic tanks scratch free.  First, clean it often to prevent heavy build up of coralline (a cleaning magnet is a great aid here).  Second, be very careful to use acrylic safe tools and don't trap any sand or grit in the tool.  Lastly, just be generally careful in how you work in the tank, place rock, etc.  There is no doubt you will get some scratches, but under water they are nearly invisible and shouldn't detract much from your viewing pleasure.  Best of luck!  Adam>

- Acrylic Scratches -
Good morning,
My question is as follows: I have an acrylic tank and while I was setting it up a few scratches appeared inside the tank and I would like to know how I could polish it, I have read about a tool called router, but I have no idea if it is the tool I need or if I could introduce it inside the water. <A router is not your friend in this endeavor and in fact the only power tool practical for such things is your own arm-power. There are a number of scratch-removal kits which involve fine grade abrasives... some can be used wet, others must be used dry. Both types are available at most online retailers. You find however that it takes longer than is practical with less than satisfactory results... you might just want to get used to the scratches.>
Thank you very much.  Jorge
<Cheers, J -- >

Can Some Fish Scratch Acrylic?
Bob,
<Yes>
I have read at one website that some fish will "mouth" the sides of an acrylic tank and make scratches.  The fish listed included angels, butterflies and triggers.  Is this something for an acrylic aquarium owner to be concerned about?
Joseph Rouse
<Mainly just some of the tetraodontiform fishes (triggers, large puffers)... but compared to other sources of scratching (mainly aquarists with cleaning tools, trapped bits of gravel...) no biggee. In the world of possibilities, this is minor spuds. Bob Fenner>

-Removing scratches from acrylic tank-
Hello, I found your site while trying to figure out what to do with my 60 gal tank.. My wife was trying to be helpful and scrubbed the inside of my acrylic tank with one of those sponges that have the green scotch pads.. <Ouch!> Needless to say, the front of the tank now has a "clouded" look to it.. We have since moved from So Cal, to Grants Pass, Oregon.. While the tank is now drained I'd like to get the scratches "polished" out.. I have read of the product called "Novus" on your site.. Is this something I can do myself? <Absolutely, and I hear it works wonders.> Or is it something I have to have a supplier apply? Is there any supplier in the Grants Pass, Oregon area that I can purchase this from? <No idea, but I did find an e-tailer that carries it http://www.tropicalfishstore.com/careproducts.htm> Any help will be much appreciated! <Good luck! -Kevin>
Thank you,
George King

Removing Scratches on tank
Hi,
<Hello there>
I love your web site (Bob along with the WetWebMedia crew, along with your book.  It has helped me so much in my years of reef keeping.
<Ah, good. Our intention>
I am, however, puzzled by one question.  Whether or not I can actually use the Novus product underwater?  
<Mmm, no... you must drain the tank down to below this point... though some water may remain in the tank... and the livestock too if there is enough space for them>
In one post you claim it can not be used, and in another you claim it can.  I have cited each for you below.  I know that toothpaste method works for certain to remove light scuffs inside the tank, I have done this several times without any ill effect.  I just wonder how safe Novus 3 or Novus 2 would be underwater, in a fully stocked reef with corals, fish and inverts.  I would hate to blow thousands or dollars just to remove a scratch.  So, which do you recommend, using Novus underwater, or not using it underwater.  Thank you in advance for clearing this up.
Jon
<Sorry for the confusion. The second piece is not clear, but it is my intention to convey that the product itself is NOT toxic if it gets into the system/water to some extent (have done this myself), but does need to be worked, rubbed-in in the air... that is, with the tank drained down or emptied. No problem with some of the resulting "dust" getting into the water though. Bob Fenner>
Taking out scratches from the inside
Bob,
Do you know of any acrylic scratch removal kit that works underwater?
<No... all require draining the system at least down to the level of the work. Bob Fenner>
Thanks, Lee
Re: follow-up on removing scratches in acrylic tank using Novus, and visit to Phoenix
Thanks, Bob, for your very prompt response!
It is comforting to know that your experience shows Novus 1, 2, and 3 can be used on the inside of an acrylic tank without harm to the fish. I bought the Novus 1, 2, and 3 yesterday afternoon.
<Wish I had made these products!>
As a follow-up to my earlier email to you, can I leave my large jardinei in the tank while I am working on removing scratches with Novus 2, and if necessary,
Novus 3. That is, from a chemically (nontoxic) safe standpoint?  
<As far as I'm aware, yes. Have used these in "full tanks", fresh and marine, with impunity>
There will be about 4 inches of water for him to stay wet;
<And not jumping out!>
the lowest scratch to be removed is an inch above this water line.
Thanks in advance for your advice!
BTW, Phoenix has a dry heat this time of year ... and its been mild this week. Its the August monsoon that you want to avoid.
Steve
<Will be out there this Thursday with some friends/associates, giving a pitch at the DMS (Desert Marine Aquarium Society). Stop by if you'd like.
Bob Fenner>

Removing Scratches From Acrylic Aquariums
I just recently purchased a brand new Sea Clear Acrylic aquarium and when I was fumbling around with my rocks in the aquarium I noticed that the acrylic was scratched rather easily.  It was very disappointing since this was a new tank.
<I can relate! I love my acrylic tanks; swear by 'em for strength, but I hate the scratch aspect!>
Scratches are rather light, I realize now that acrylic SCRATCHES very easily.
<Yes, it does! Be careful, also, if you use a magnetic "algae scrubber", and have a fine bed of sand. These magnetic scrapers can pick up bits of sand on the pad and leave full-length scratches! I know, 'cause I've had it happen, myself!>
My question is, is there any way to remove light scratches on acrylic or are they pretty much permanent?  Is there any method or product that I can use or a web site that you can refer me to that may help me out with removing these unsightly scratches?  Thank you very much for any information you can provide.  Love the site.
<Well, there is an "acrylic scratch removal kit" by Rainbow Lifeguard (now Pentair Aquatics), that you can get online from Dr. Foster & Smith, among others, which consists of varying grades of fine grit sandpaper, used one after the other, getting progressively finer. It takes a lot of patience, and you must be very careful, but it does work. Hope this helps! Regards, Scott F>

Acrylic tank
Hello, <Hi Audrey, MacL here with you today.>
Sorry to bother you but I found you on a search and wanted to ask you a question. I just bought a used Acrylic 60 gallon tank. I was so stupid and cleaned it with a ......... and now my tank is very dull. <Acrylic tanks get scratched extremely easily and some chemicals "burn" them.  Its pretty easy to restore the shine though. I'm assuming the tank is still empty. I personally have had good luck with the Novus products. They have several types of polish.> What do I do??  <Find a plastics store in your local phone book and ask them if they carry the Novus polish products. I think you are going to need all three of them to bring back your tank.> Please help me. <Hope that helps. MacL>
Thank you,
Audrey

Toxicity of Sea Clear acrylic scratch remover
Is Sea Clear acrylic scratch remover toxic to fish-can it be safely used inside the aquarium to remove scratches?
Thank you,
Sue Kennedy  :)
<Not very toxic... so okay to have bits fall into the water, but best to lower your water low enough and remove the residue after rubbing as much as possible. Bob Fenner>

Picture of crazing I read your Q and A section about acrylic aquarium repair and my question was about crazing.  Mr. Fenner stated that one should take a picture and ask an expert to take a look at it so what do you guys think??? <This is... crazing for sure> should I scrap it or is there some way to repair this monster it's 240 gal standard this is the only real tank flaw it's about 3 or 4  years old. please tell me I can fix it      <I wouldn't scrap the tank... for fear of it rupturing... if this is all the apparent stress cracking there is. If it worries you, solventing a thin sheet/piece of acrylic over the area (with the tank empty) may render the crazing less conspicuous while adding strength. Bob Fenner>

Re: picture of crazing Thanks so much I really appreciate your advice I think I am going to melt a little acrylic on there you can't really see it when the hood's on. my concern was more structural.     Thanks again Mr.. Fenner <You're welcome my friend. Bob Fenner>

(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>