FAQs on Acrylic Aquarium Repair and Modifications: Design and Engineering

FAQs on Acrylic Aquarium Repair and Modifications: Design and Engineering

Acrylic and HI! 6/30/17
Thanks Bob,
<Hey Tom>
So I just wanted your thoughts…..the acrylic tank is 4 foot high, 4 foot diameter and the top and bottom are 1 inch think but the actual cylinder is maybe only 1/4 -1/3 of an inch….
<...?! MUCH too thin material all the way around. I'd make the bottom 2" and the cylinder and top a minimum of 1.5" material. This tank was NOT made to hold water>
the welds are also full of bubbles and as expected, it popped at the bottom and leaked…I actually feel like it is a liability for a public display..
<It is Tom; I would NOT fill this tank... perhaps turn into a paludarium, terrarium... a partial (foot or so depth) water and land display?>
Anyway, might be worth a rebuild with reinforcements on the inside (including the seam!)
<Can't be reinforced enough to make into a safe/water filled display. Too dangerous. Am having some tanks bid by Waterdog (.com) here in San Diego, including some cylinders. Write or call John Harriman there Re if you'd like more input.>
Will you be at MACNA?
<Ah yes; working on my (anemone) presentation. Hope to see you there. Cheers, Bob Fenner>
T

100 Gal. Acrylic Tank Modifications - 10/25/05 Hi Bob, <<EricR here...>> I got your email address off of the web by searching for information on Acrylic tanks. <<Much info about many things "wet" here.>> I have a 100gal (60x18X20) TruVu that I have had now for maybe 6 months. I am getting into the final stages of this all set up and just about ready to fill it. <<Ah...anticipation!>> One small problem... I have two Emperor 400 power filters I am going to run on this. Standing on a ladder looking down at the tank, on the top in the back of the tank there are two cut out areas behind where the lights would sit. I was planning to put my filters here but I need 16 inches total across for the filters to fit. In order to do this I need to take less than 2 inches off each of the areas where the filters would hang. So I was thinking a 1/2-inch on each side of each cut out area to get the filters to fit. If I do this, will I be possibly taking away from the structural integrity of the tank? <<Maybe...though what you describe doesn't sound unreasonable if done with care.>> It's not allot I will be taking but what would be the max of that area that I could take? <<Hard to say...will depend on acrylic thickness, skirt width, other design features.>> Any advice would be greatly appreciated! <> Thank you <<Regards, EricR>>

Re: 100 Gal Acrylic Tank Modifications - 10/27/05 Hi Eric, Thank you for your feedback, appreciate it. <<A pleasure>> I looked again yesterday and the amount of space I need on each side of the filter areas is less than a half inch each side. I plan on NOT touching the center support area at all so I think this should be okay. <<Likely so>> It appears that the thickness is approx 1/4 inch or more. <<Mmm...Hopefully more...>> So like you said I will have to do this with care.. :) <<Careful use of a Dremel-type tool and appropriate bit is a good method for removing this small amount of acrylic.>> Thanks again and I enjoy your web page and information I have been reading. <<Happy you find it useful. Regards, EricR>>

Acrylic aquarium: repair necessary RMF's go I just purchased a lightly used reef ready 110 gal tank 48L x 30"H x 18"D. When I filled it, I noticed that the front and back bow out by about 7/8" <A bunch... is this a stock tank... by whom?> without the salt added (don't want to pour $60 out the window!). It is well supported on the top with .5" acrylic but the sides are only about 3/8". <Should be structurally okay for a tank of this height, run... but half inch would have been better aesthetically> The front corners are rounded by about a 2" diameter. All the seams look good and solid but on the bottom right side, there are some light lines, they look like crazing but are mostly parallel and are invisible head-on. There was a mention of this sort of thing in Mr. Quattromani's Acrylic Repair article, but I'm not sure from the article of what to do beside trash it and buy another tank. I wish I read it before I bought! <Mmm...> The owner of the local pet store builds tanks for his personal use, when I asked him, he said that it would probably but not certainly be fine for quite some time, but that if I'm worried, I could greatly reinforce the seams by attaching a strip of acrylic to the tank along all of the seams. Agree? If it would likely be okay for a year or two as it is, that would be perfect as I'll be moving in that time and just buy a new tank at the new location and transfer the livestock. If not, would the patch be okay? Just to be clear, I understand you cannot make promises. <If the crazing is minimal as you state, even though it is bowing this much, this tank, set upon a good bottom should be fine. I would very likely use it and not worry. Bob Fenner> Thank you, -Rob

A Poorly Engineered Acrylic Tank - 04/22/06 EricR's go I just purchased a lightly used reef ready 110 gal tank 48Lx30Hx18D. When I filled it, I noticed that the front and back bow out by about 7/8" without the salt added (don't want to pour $60 out the window!). <<Yikes! That is a lot of "bow">> It is well supported on the top with .5" acrylic but the sides are only about 3/8". <<Mmm, poor engineering in my opinion...the sides (and top!) should be twice this thickness (3/4") for the height of this tank>> The front corners are rounded by about a 2" diameter. All the seams look good and solid but on the bottom right side, there are some light lines, they look like crazing but are mostly parallel and are invisible head-on. <<Not uncommon>> There was a mention of this sort of thing in Mr. Quattromani's Acrylic Repair article, but I'm not sure from the article of what to do beside trash it and buy another tank. <> I wish I read it before I bought! <<Indeed>> The owner of the local pet store builds tanks for his personal use, when I asked him, he said that it would probably but not certainly be fine for quite some time, but that if I'm worried, I could greatly reinforce the seams by attaching a strip of acrylic to the tank along all of the seams. Agree? <. There's a store here in town with some "plant" tanks that were made similar to yours...lots of bowing can be seen from the sides...and they have been fine for several years...thus far. But were this me...I would relegate your tank to sump/refugium duty where the water volume would/could be limited to about half the tank height>> If it would likely be okay for a year or two as it is, that would be perfect as I'll be moving in that time and just buy a new tank at the new location and transfer the livestock. If not, would the patch be okay? <<Is "likely" to be fine either way. Is up to you to decide if you want to take the gamble...I would not>> Just to be clear, I understand you cannot make promises. <<Indeed my friend...but I'm pretty sure you will never be "quite satisfied" with this tanks appearance, if for no other reason>> Thank you, -Rob <<Anytime, EricR>>

Re: acrylic aquarium: repair necessary There is no manufacturer listed on the tank but judging by the way it's supported on the top and the overflows and such are done, it looks pretty professional. <Ah, good... and the fact that you state the corners are/were heat-bent is further proof> I am very nervous because I keep hearing different things. I've done a lot of asking around and I've heard everything from "Picture a grenade full of fish, pull the pin--what will happen?" through "enjoy the tank!" <Mmm, one thing you might do that might bring/grant you piece of mind is to fill the tank outside... in the garage perhaps, and leave it full there for a few weeks... It really should be fine. Bob Fenner> Right now, given such mixed answers, I'm leaning toward selling it cheap as a giant terrarium or breeding tank for a basement and buying a more modest 75gal glass as I live on the 6th floor and wouldn't want to flood the neighbors. -Rob

DIY/Acrylic Weir 1/22/07 HI <Hello Andy> I'm interested in building an acrylic weir for my 4 by 2 by 2 marine tank and I have a few questions: The weir will be in the back left hand corner, going 6 inches along the back and 12 inches along the left hand side. I have decided on this size so I can drill holes through the acrylic and position powerheads through them, thus hiding them and making maintenance easier, while still having room for the inlet to the sump. 1) the tank is made from glass, will the bond between the acrylic and glass be strong enough? <Yes.> 2)Im in the UK and have only found acrylic for sale that's 5mm thick, would this be strong enough? (I know acrylic is stronger than glass but the tank is 12mm glass) <Will be strong enough.> I could make the weir from glass but acrylic is easier to drill, so that's why am interested in it. Any help you can give would be greatly appreciated. <Should have no problems. Do use an adhesive designed for aquariums. Some Silastics have mold inhibitors which can cause problems with your livestock.> Thanks <You're welcome. James (Salty Dog)> Andy

100 gallon acrylic tank bowing Hi there, <HI> I have what may be a silly question for you guys. We just upgraded from a 30 gallon glass tank to a 100 gallon acrylic tank. We've got all the equipment setup and working, the tank is full, and we have noticed that the front and back seems to be "bulging" out about an inch or so. We figure this is probably normal due to the weight and flexibility of Plexiglas, but are somewhat paranoid - that is a lot of water in there! <It sure is a lot of water, and I would not want it on my floor. Acrylic tanks will bow a little bit, but an inch sounds dangerous to me. I would drain the tank and install a brace, possibly a padded bar clamp. We have some FAQs on acrylic tank repair you might want to check out. http://www.wetwebmedia.com/acrylicaqrepair.htm http://www.wetwebmedia.com/acrylictkrepfaqs.htm > Can you tell me if this bulging is normal or if we should be worried about the impending flood? <I'd worry, I tripped over a 5gal bucket dumping water all over my floor, and that was a pain to clean up, I would not want to imagine 100gal. -Gage> Kristin, BC, Canada

PLEASE HELP!!!! <Acrylic tank coming apart> I am panicking big time! I wanted to check with you to see if you had any ideas or suggestions. I have a 160 gallon acrylic tank. I got it about 6 months ago on EBAY and it has been absolutely wonderful. It looked very well made with the top being completely molded into the frame with just two cut outs as openings. It is not leaking at the moment but yesterday I saw something very disturbing happening. It looks like there is an extremely very slight separation in the seam of the side wall coming into the back wall. The separation is on the outside and air is getting into the seam. I feel no separation at all on the inside. No leaking water yet so it has not made it through the 1/2 acrylic to the inside I'm assuming. It started at the very top and is moving down quite rapidly. . . it moved about 1/2 inch during the night. I'd say from yesterday morning to this morning it is about 4 1/2 to 5 inches long. You can see it clearly looking in from the front of the tank because the air is reflecting light. Like I said so far no water leakage at all. We put clamps on it this morning because I just had nightmarish visions of the entire house being flooded when I went home from work. Were clamps the right thing to do? Have you ever seen this happen before? <Have seen this happen before... the "whiting out" or crazing area is very bad news. DO IMMEDIATELY DRAIN the tank down at least half way. It may well separate at this seam!> Am I freaking out for good reason or overreacting? I'm guessing that I will need to get a new tank right away. . . so, I've looked into it and it will take approximately 2 -3 weeks for the store here to get what I need in. I'm just hoping that the clamps will hold!!!!! As far as what tank to get. . . I loved acrylic for the reason that it seems so much more durable than glass. . . but since this has happened I don't know. Would a 160 gallon glass tank be too dangerous -- should I keep going with acrylic? <Both are "reasonable" (safer than driving on the road) technologies> One other reason I found that I don't like acrylic is that it is so difficult to clean without scratching. I hate that but have put up with it because of the durability. <Yes> Can you offer some much needed advice? If I did go with an all glass tank what brands do you recommend? Is All-Glass on your list? <Yes... as well as Perfecto, Oceanic... in the old days Atlas, Odell> Also, please tell me if you would go with acrylic again for the durability. <We mainly fabricated and installed acrylic in Southern California... due to earthquakes... their greater strength during "shaking". Bob Fenner> Thanks so much! :)
Acrylic Tank coming apart I've checked into it and I will have to wait 3 - 4 weeks for a replacement tank. I'm am so stressed at the moment I don't know what to do. If I drain the tank to below the crack I can't run the pumps. How long can my fish safely live without a filtration? P.S. I also have live rock. What to do???? HELP!!!! <Think on ways to add a sump (even a plastic tote) where you can place some of your live rock, run the water back and forth. But do drain the tank down> Thanks for any advice you can offer! :) <Will your local fish store your livestock for you while you await the replacement tank? Do ask. Please see here re moving, storing your gear, livestock: http://www.wetwebmedia.com/movingaq.htm Bob Fenner>
Acrylic Tank coming apart RE: PLEASE HELP!!!! (quick suggestion from Ananda) <Ananda here, hoping to lend moral support...> I've checked into it and I will have to wait 3 - 4 weeks for a replacement tank. I'm am so stressed at the moment I don't know what to do. If I drain the tank to below the crack I can't run the pumps. How long can my fish safely live without a filtration? P.S. I also have live rock. What to do???? HELP!!!! Thanks for any advice you can offer! :) <I'm going to let Bob answer, too, but I thought I'd pitch in with a suggestion. You could use 55 gallon Rubbermaid Brutes (the grey, white, and yellow ones are food safe) to hold some of your rock and water (and maybe even some of the fish -- don't know which species you have) until you get a new tank. Hang in there! --Ananda>
Re: PLEASE HELP!!!! <Acrylic tank separation) Hello again. . . was hoping you could give me some more pointers. Here's what I've done so far. I've drained the 160 gl tank down to well below the crazing (however it still keeps creeping!) <Keep draining till it stops> and have transferred the fish to a 75 gallon and have hooked up all of my equipment (wet/dry, skimmer, sterilizer, etc.) to this new 75 gallon. I transferred some of their substrate and rocks too. They seem to be doing fine however I'm worried that they will think they are being punished for going to such a small tank!!! Will this stress them out? <Not as much as living w/o water> I've adjusted the flow rate (a Mag 9 is running the wet/dry) and have turned it down about a 1/4 of the rate it was going. Is that enough or is the flow rate too high for the 75 gallon? <Should be fine> Here's my dilemma. My VHO's and small power compact are hooked to the 160 gallon so I left a little water in there for the live rock and a pump circulating the water so that they could receive the benefit of the lights because the 75 gallon does not have any at the moment. <Good plan> Will the live rock survive with just the circulating water and lights for 4 weeks. <Also should be fine> I couldn't add the Kalkwasser and calcium because there is no filtration, right? Or, would it be better to somehow rig up a little power compact to the 75gallon and transfer the live rock in there with the fish? <You can measure calcium, pH and add supplements as you see fit> Will my excess water (that I really want to save since I spent months getting it perfecto!) that is being housed in large plastic containers and some in the old tank be ok for 4 weeks with just a circulating pump? Will it still be perfect with no fish being in it for 4 weeks? <Yes> The new tank will most likely take the full 4 weeks. I've ordered another acrylic (has a lifetime warranty) from a reputable company (been in business 20 years) and have ordered the following dimensions: 72L x 18w x 34h -- is this ok as long as the acrylic is 1/2 inch? <... 34 inches tall? I hope your arms are long... I would have preferred either thicker material (mainly to reduce the degree of bowing and improve looks, looking through...) or to have made the tank wider, but shorter... to work on, support life> Would it be better to go with 3/4 inch? The 160 that cracked was 1/2 inch and was 72 x 18 x 28 so I'm just going 6 inches higher. <Yes to the 3/4 (call and change if possible... NOW), six inches higher is a huge difference> Sorry to be so long winded but I have lots of questions -- hope you are full of patience today! :) <No worries> Trying to figure out why the crack happened in the 160. What could have caused this? <Almost assuredly construction defect... the folks who cut and assembled the tank didn't make joints square, clean, did solventing in a high humidity (very common), or used defective solvent...> The tank was perfectly (I mean perfectly) level and I use VHO lighting (4 ft. bulbs centered across the 6ft tank) as well as one small power compact in the center. I know MHs aren't smart to use with acrylic but I always thought VHOs were fine. . .am I wrong? The crazing happened in the right back corner where the VHOs are really over it???? Any ideas of what happened? <Not much chance it was the lights, or anything you did... as stated, it is/was the manufacturer> Last question I promise!! I was thinking of adding an angel fish before all this happened. Would it be better to let my fish get acclimated to their new tank when it arrives and add the angel a few weeks after or should I add the new angel at the time they go to their new tank so everyone is claiming new territory? (I'm thinking the Angel will need to go in a few weeks after the fish have acclimated so it won't get the "I'm the king of the tank" attitude and might be a bit humbled?? Thanks for listening to me babble. . . I appreciate you more than you know!! Would welcome any advice you care to give. Thanks again! <Bob Fenner>

Tank coming apart follow-up Hello again. . . just a little update on the situation. . . all fish are doing fine and are acclimating nicely to their smaller 75 gallon. All of us are anxiously awaiting the arrival (still have three more weeks to anxiously await) of the new tank so our lives and living room can get back to normal. By the way, THANK YOU for all of your help during my crisis. I literally don't know what I would do without you!!!!! (PLEASE, don't ever get out of this business/hobby!!!!) :) <Not likely, thank you> A quick question. . . I've, of course, been keeping my left over water that wouldn't fit into the 75 gallon in large Brute trash cans in the living room with the base rock in there and pumps circulating the water. One trash can sat for about a day without circulation -- is that water ruined? <No, should be fine to use.> Secondly . . . . I've transferred all of the sand (not live sand) into buckets. They have a little water sitting on top but are not being kept in the huge trash cans being circulated. Is this ok? <Yes> Last question. . . I had been using a MAG 9.5 to run my 160 gallon. I've been using it as an external pump (it seems to be working great) but recently read in a MarineDepot.com catalog that MAG pumps are not to be used externally. Is this your opinion too? What would happen if I continue to use it externally? <It may overheat, quit on you, but there are others who have used this size, line pump externally with impunity> But, this may be a moot point when you hear my next question. Since I am going 6 inches higher and 30 gallons more with my new tank coming in will a MAG 9.5 be sufficient to run this fish/live rock only tank? What if I wanted to start slowly getting into corals (have VHO/PowerCompact lighting)? Would I need a larger pump now for the extra height and gallons (if so, please recommend some) or only if I were to go with more of a reef system? Thanks for your advice! <It may be time to upgrade then> I think that's it for now. Again, A HUGE THANK YOU!!! You are truly a lifesaver!! By the way, do you ever come to Tallahassee and lecture at Florida State University? <Have not yet. Bob Fenner> Elizabeth

Acrylic Wall Thickness for Large Tank 7/17/04 I am building a very large tank in the shape of an equilateral triangle. The dimensions are 24 feet long by 8 feet to the point of the triangle by 4 feet high (or deep). It will be placed on a strong 18 inch concrete floor. I am guessing that 2" for the sides and 1 inch for the top and bottom should hold well but I am just basing that on my limited engineering experience. Do you know how I could find out if these dimensions will be OK. Can you recommend any structural engineers if I need one or is it not that complicated if I know how to figure it out. Thanks Dimitrios <Hi Dimitrios! I hope when you say that you are building this tank, that you mean you are having it built. This is not a DIY project! I would begin by contacting some of the following: A large public aquarium, Reynolds Polymer and San Diego Plastics. I would consult a structural engineer about the floor. A public aquarium should be able to direct you to large tank manufacturer (SD Plastics is one, but this project may be beyond even their capabilities). Reynolds polymer makes very large, very thick acrylic material for public aquariums. They can probably direct you to a manufacturer that deals in large display tanks. There are wall thickness calculators on the 'net for acrylic tanks, but they only apply to rectangular tanks. Good luck! Adam>

How much bow in an acrylic tank is normal and safe? I've recently obtained a used 55 gallon acrylic tank and it really bows. The tank dimensions are 48x13x20. When full of water the front bows out 5/8" and the back 1". <This IS quite a bit... for this thickness material, though acrylics do vary somewhat... and somewhat unsettling in that the bulge isn't about the same front and back... But, not totally out of order, and very likely nothing to worry about> I'm trying to determine if this is safe to put in the house or not. <Should be fine> Your thoughts or maybe where I can turn to get an answer... Todd M Howe <Bob Fenner>

Acrylic Questions 3/30/05 You guys have been great so far (in the FAQ's an in responding to me). I have two questions about acrylic. <Glad you have benefited!> 1) I bought a 120 gallon Tenecor pentagon corner acrylic tank, stand and canopy setup from someone. The overflow tower is 4" shorter than the height of the tank. Don't I want the tower to extend to the top so I can avoid an unattractive water line 4" below the canopy? What do I need to do to extend the tower to the top? I assume I will somehow bond acrylic over the current slits and make new slits at the top of the extended tower. Since it's not an area that will bear much weight, should I just use silicone? I'd like it to look decent. The tower is black, but I don't mind clear acrylic extending upward. <If you can, I would ask the previous owner about this. Some tanks come with adjustable "Dams" that allow the user to adjust the water level. Look for a screw hole in the overflow as a clue that such a device may have been included. Even if it isn't bearing weight, silicone is a very poor adhesive for acrylic. A small tube of Weld-on #13 is very inexpensive and nice to have on hand for DIY projects. Every major city has an acrylic supplier, and most have a "drop bin" where you can buy assorted small pieces for bargain prices. Be careful not to make it too high to avoid spills!> 2) The canopy has 4 small acrylic pieces bonded to the underside for lighting, but the lighting I need to do doesn't fit the slit shape and they are 1/2" thick (two 1/4" pieces, I think). I can't fit my lighting in there without the surface being flush. Is there any easy or possible way to remove these pieces? <You will have to do this very carefully. The solvent bonds between acrylic pieces can be stronger than the material itself, and there is a great deal of risk of breaking the canopy. Home Depot and other hardware stores have special "flush cut" saws. An El-Cheapo one is less than $10 and will allow you to cleanly saw off the tabs without risking cracking the canopy.> Any help would be GREATLY appreciated. My setup is on hold until I figure this out. Peace, Clint <Good luck! AdamC.>

- Acrylic Tank Modifications - Hi guys, I purchased a used acrylic Tenecor 180 gal. RR tank, drilled for a closed loop and overflow mounted outside the tank. Sweet configuration (and in great shape). The top is made of 1/2" acrylic and has 3 cutouts. I have seen acrylic tanks with Euro Bracing and I like the open access for the lights and working in the tank. My question is: If I cut the two braces between the cutouts, do you think the remaining acrylic would act as a Euro Brace and support the load without bowing and cracking the tank? <I'd be cautious. You would likely need to add additional bracing to create a true "Euro Brace". Given that I've only ever seen this type of bracing on glass tanks, I'd be hesitant to tell you this will work on an acrylic tank.> <<RMF would NOT do this>> The tank measures 72" x 24" x 24". The remaining border would measure 6" wide from front to back (left & right sides) and 4" wide side to side (across the front and back), one solid piece of 1/2" acrylic (or do you think the 1/2" needs to be thicker?). I realize there are no guarantees on opinions, but I really hope this could work. The Euro Braced tanks I looked at had 4" borders all the way around. <Of what thickness material on what size tank? Given the length of your tank, the center brace helps stop the center of the tank from bowing, and without this brace I think you might see not only a noticeable bow in your tank but the remaining bracing would also bow and crack. Would for certain test out in the driveway first before adding anything you care about.> Waiting for your opinion with saw in hand...... Scott B. <Cheers, J -- >

Acrylic tank repair question 8/1/05 Hello, I have a question. I am looking to buy a 300 gal sea clear tank. I found a used one locally that has only been set up for 1 year. Selling price $ 400.00. <Wow! What a steal!> Here is the catch. It has a .5 x1.5 inch separation in the front panel where it meets the side. <Darn! There is always a catch! And this one doesn't sound good.> It is not leaking and was like this with no change for 3 months while the owner upgraded to a larger tank. The tank is empty and has been so for 2 weeks. Can this tank be repaired? I don't know where the line is for safely repairing such a large tank (don't really need a swimming pool in my room.) Would be a great deal as my two angels have out grown their home now. I want to make a smart decision with this not only for me but also for the angels, as I don't want to see them surfing the carpet. Any input would be greatly appreciated. Addicted to your site, Erik Lobe <This could be repaired by a qualified acrylic shop, but most would probably not want the liability. It is probably not likely that the tank will fail. Unfortunately, if it does fail, it probably will not develop a leak... it will fail catastrophically. As a long shot, you may want to contact Sea Clear and see if they will honor a warranty on the tank if you buy it. You might be able to buy the questionable tank and get it replaced with a brand new one. Be sure to get documentation of the original sale from whoever you are buying it from. Best Regards. AdamC.>

Acrylic Tank Mods Gone Wild 7/21/05 Dear WWM Acrylic Tank Mod Guru : <Mmm, must be all the methacrylate stains on my clothes, the absence of nasal hair...> I think I know the answer to this question already (don't do it!), but here it goes: I have a 135 gal acrylic tank, 72" long, 24" tall and 18" front to back, 3/8" thick, made by TruVu. I want to cut the top completely out (!) and brace around it with very strong wood and steel, kind of like a picture frame if you were to look at it from the top down. This brace would be an integral part of the stand and canopy I am making. I've searched WWM for questions and FAQs on this but can't locate any. Any input is appreciated : if you say don't do it under any circumstances, please enlighten me as to why. thanks, SLC <I wouldn't do this... surprised? You might router out most all the current top... leave a good four inches around the perimeter and the same for the material across the top... but the top is an integral part of the whole structure... and won't be replaced with a frame on the outside. Bob Fenner>

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