Please visit our Sponsors
FAQs on Glass Aquarium Repair, Silicone/Silastic... Aquarium- Use 100% (Aquarium Use) ONLY,  4

Related Articles: Aquarium Repair, Acrylic Aquarium Repair, Cleaning Aquariums, Marine Tanks, Stands and Covers, Used Gear for Marine Systems, Designer Marine tanks, stands and covers,

Related FAQs: Silicone/Sealant/Sealing 1, Silicone/Sealant 2, Silicone/Sealant 3, & Silicone/Sealant 5, Silicone/Sealant 6, Glass Aquarium Repair 1, Glass Aquarium Repair 2, Glass Aquarium Repair 3, Glass Aquarium Repair 4, Glass Aquarium Repair 5, & FAQs on Repairing Glass Tank: Scratches/Blemishes, Cross-Braces, Leaks, Chips/Cracks, Whole Panes, Tools: Cutting Glass, Moulding/Frames; Techniques; Olde Tank (Slate Bottom, Metal Frame, Pecora...) Repairs, Troubleshooting/Repairs, & Acrylic Aquarium Repair, Used Aquarium Gear,

Chips in 240gal Tank     8/13/13
Hi guys,
I've been poring over your site for the last couple of days and haven't managed to find a problem that really fits 'exactly' with the problems I have.  I may just need to do some more digging.
<Mmm, if you scanned through all the chipped glass tank repair FAQs you're done>
I acquired (about a year ago), a 240 gallon, custom aquarium, approximately 24"w x 32"T x 72"L, made form 5/8" glass.  It has a built in overflow that uses 8" of one end of the tank and has euro-bracing around the perimeter of the tank.  It does not have a cross-brace.
<I would add one (a foot or more wide) in the "middle"; on top or bottom of the (doubled) Eurobraces already present (and chipped/broken)>
 This tank, as you can imagine is a beast to move and was treated rather roughly by it's previous owner during moving due to lack of planning and too few hands  (cost one of them a finger). 
The trim on both ends of the bottom were torn off.  On one end, the glass escaped unharmed, but the other wasn't so lucky.  In the picture attached, "bottom_corner_chip", you can see the rather large chip on the bottom pane.
<Yes; but/and this doesn't look/appear "too bad">
There's also a sliver chipped off the opposite end, at the top, just below the trim.
<I see this as well>
In addition to those, the bracing has broken and cracked in the center on both long edges.  I think those were more due to the stress of holding the water and had less to do with moving.
<Mmmm; I hope/trust due to something other than holding water>
Alas, I really want to set this tank up.  The silicone looks a little rough in a few places and discolored (orange/brown color) in others and I would really like to 'not' have to reseal this monster if I don't have to.  It would be my first time and I'm not terribly confident I wouldn't make it worse.
<I would try it as is; then as the next level of repair, cut out and replace the corner seals... LASTLY I might attempt cutting out the between glass, cleaning up (w/ Toluene likely) and completely re-assembling... But more likely would turn into something other than an aquarium...>
The tank was originally used as a saltwater tank, and has not yet been cleaned.  I intend to use it for African Cichlids and upgrade their living space.
I intend to set this up in my garage prior to moving it inside the house to its final destination, but I would rather get it repaired before putting water in it to even bother trying to test it. 
<Good. I would go this route as well>
Moving, as stated before is an issue and requires minimum 4 people and lots of luck, so the fewer times it gets moved, the better.  It's currently sitting on 2 furniture dollies, with 2x4's under each end so I can move it around while cleaning it, but flipping and lifting requires planning.
So my question is, can this be repaired to a point where it wouldn't explode?  If it can, what's the best method of doing so?
<I would try simply "filling in" the external gaps/chips with Silastic (to prevent hand cuts), and do the repairs/additions mentioned above... Easy (even fun!) to add the bracing atop or below the extant... and the front/back brace piece on top or below the long run braces>
Thank you in advance,
<Glad to assist you. Bob Fenner>

Re: Chips in 240gal Tank     8/13/13
Thank you very much for your quick response.  I'll make the suggested repairs and let you know how it goes.
<Thank you, BobF>
Thanks again,

Re: Chips in 240gal Tank; plus bracing and resiliconing     9/4/13
Hi Bob,
Thanks again for your previous help, but I have some more questions and I wanted to compare ideas a little.  I talked to someone that works at/for glasscages.com.  He suggested that I go with 2 center braces, vs. 1, even if they're smaller.
 He said, "Two braces are always better than one."
<I do agree with this statement; just the more there are, the harder it is to get "stuff" in/out of the system, catch livestock... at some point, having more braces/bracing is of not much more benefit>
  I just wanted your opinion on doing (2) 4" wide or 6" wide vs. (1) 12" wide as previously suggested.
<... also; "the wider the braces the better"... w/ same comment re "diminishing returns">
  My plan is to put a cross brace or braces between the existing bracing, and then laminate a second cross brace on top of it with the rest of the laminated bracing.
He also pointed out that they build theirs with euro bracing at the top and bottom of their tanks.  I like the "idea" of doing the euro bracing at the bottom as well, however, I'm leery about doing any cutting on the existing silicone.
<Mmm, this isn't really a big deal... a bit of work (look into tools for holding on to single edged razors), but can be done leisurely; not all at once>
 From what I've read on your FAQ's, I would have to cut the silicone out of the corners, being careful not to cut in between the glass panes. 
<Yes; and again, not hard to do>
If I do that though, will I not have to replace 'all' of the silicone in the rest of the seams as well?
<You will not have to replace the rest; no>
 My concern would be tying into the silicone on the vertical seams if I only cut out the bottom silicone where the bracing would go.
<The "in corner" Silicone is not functional in terms of holding the tank together (not much anyway), but really to protect the "between glass" Silicone...>
Another concern would be physically crawling into the aquarium to work on the bottom of it.  I know the water puts a lot more pressure on the glass that I could, but it's spread out over the whole pane.  Would me (155 pounds) crawling around in the aquarium hurt it, so long as it was resting on a blanket to keep from scratching it etc.?
<Yes; assuredly... Though I'd likely have friends help tilt the tank on the face, back and just enter it this way; rather than crawl inside>
  It's 30" deep, and to work on the bottom, I would have to crawl in.
Thanks again,
<Welcome. BobF>

Assistance please; Killing Seastars, flooding the floor     8/1/13
<Hi there>
I inherited a 57g saltwater tank about a month ago. It included LR and LS and I kept about 15g of the previous tank water.
<A nice gift>
A few days ago I added some peppermint shrimp, crabs, Nassarius snails, and a sifter starfish. All appear to be doing well except for the starfish. 2 nights ago, he disconnected one of his legs.
<Too soon to add asteroids. Common beginning of their all-too common loss.
See WWM re the species>

 I've read this can be due to stress and a defense mechanism. He hasn't moved much and as far as I can tell hasn't eaten. I isolated him in a Tupperware container in my sump so that I can place some flakes in front of him.
<? What species is this?>
I had to isolate him because the shrimps kept pulling at his open wound. He hasn't moved there either and hasn't eaten the flake. Is there anything I can do to help him? Poor guy.
<Keep reading>

Also, my tank has some kind of stain along the bottom edges on the silicone. No one seems to know what it is.
<Is evidence of imminent failure sorry to state... You should take this tank down... READ re resiliconing it... new inside beads (which this doesn't have) at least, or perhaps just replace. Is a bunch of work to take apart...>
 My guess it has something to do with the sand since the stain is on all of the silicone at the bottom and up about 3-4" high. Any ideas?
<Oh yes; have seen on quite a few occasions. I suspect "it" is at least partly biological... but this seal is going>
Thank you,
<In future, adhere to our stated limit on image file size. Bob Fenner>

Silicone thickness cure    1/10/13
I am planning to build an all glass tank that will be 33 inches high and my glass is 18mm. I am wondering if you know how to get the silicone to cure all the way.
<Just time going by... a few days>
What I mean by that is if the glass is 18mm than the silicone has to cure 9mm from each side but I think silicone only cures about 5mm  so 10mm thick bond maximum.
<Mmm, no; will cure at most all thicknesses in time. Used in buildings at much greater thicknesses>
 I know people bond thicker than 10mm but I don't know how. I don't want to build another acrylic tank because the urchins wrecked it after a few years. Any help is appreciated.
<I'd wait three days or more before test-filling. Bob Fenner>

vertical seam- bubbles, peeling, roughened
Silicone Seal - Needs Fixing?  -  12/29/2012

The vertical seams on one side of my 75 gallon tank are rough to the touch (as compared to the smooth inside seams on the other side of the tank) and have developed some bubbles. Small pieces of the silicone have come off the outer edges over the glass.
<This description seems unclear to me....  And not detailed enough to have a strong idea of the trouble....  However, silicone coming off of the outer part of the glass isn't necessarily an issue.  The silicone on the inside of the tank is what's important.  Silicone on the outside is usually just from a slightly sloppy job.>
There are no leaks.
<Well, that's definitely the most important part!>
The seams are near a window so don't know if this caused this problem or not.
<Most silicone sealants used shouldn't be too affected by sunlight or temperature changes, except perhaps over a great deal of time.>
Anyway, I was advised to use a razor blade and cut off the silicone covering the inside glass but not the silicone in the middle between the glass panes of the affected seams. Then put new silicone over each seam and smooth out. Do you agree with this approach? Will this make the seams worse as I read new silicone will not attach to old so it won't attach to the
silicone between the glass panes.
<If you do remove the old silicone and re-seal the tank, the "right" thing to do is to remove all the existing silicone and re-seal completely.>
Also was told I would not have to wait the usual 48 hours or so to cure since this silicone is not holding the structure together but acting more like a gasket over the center.
<I would definitely NOT try to rush this....>
Maybe could put water back in after a few hours.
<No, certainly not.  Silicone, as it cures, releases as a byproduct either acetic acid or other even more harmful chemical compounds.  As the acetic acid is released, the pH of the water in contact with the silicone would decrease, possibly to the great detriment of anything trying to live in it.
 And I assume, if you're rushing to put water back in, it's because you're keeping fish in the water.  Don't do this; always allow silicone the proper amount of time to cure - longer than the recommended time, even, if possible - and always rinse the tank thoroughly and then fill, allow to sit overnight, and check for pH changes.>
Any recommendations of what to do?
<Just as above....  And, "if it ain't broke, don't fix it".  Perhaps even consider having someone who has constructed or re-sealed tanks before take a look at the existing seal, and see if it really needs anything done or not. 
Best wishes to you,  -Sabrina>

Plywood Glass DIY   12/29/12
I was reading through some of the DIY Q and A you guys have and it seems I should just ask if this is a good idea I have in my head.  I have an old 55 gal tank, with 1/2 inch think glass,
<Wow! This is an olde one... more recent commercial tanks of this "size" (model...) have been made of 3/8, 1/4, even thinner glass>
that was given to me, that I tried resealing with silicon, and it didn't work.  I can see the seam in the corners coming undone. 
<Mmm, did you thoroughly cut out, clean the corners ahead of Siliconing? Does this tank have a frame?>
So I thought I might take it apart and reconstruct it using ply wood, but using the four sides of glass to see in at all sides, rather than just one viewing side.  I'm a little worried about it all breaking apart if I did that, so I'm asking you guys what you think!
<Well... you don't need the plywood, or any frame to construct a 48 by 13 by 22" aquarium of 1/2" glass... a brace, (Euro if it were up to me) is requisite... I'd keep reading for a while here before settling on a plan of action. Bob Fenner>
Re: Plywood Glass DIY   12/29/12

I did cut and clean the old silicone 2 or 3 times before applying the new stuff.
<... what solvent did you use to clean the glass? Have you read on WWM re such re-siliconing?>
 it still had a VERY small leak that ran down one of the seams in the corner.  I am quite nervous about re-doing the inner seams of glass, which is why this idea seemed the best to me.  But if you think I can do it, could you point me in the right direction (FAQs and the like)? Thanks.
<Ah yes. Please start here: http://www.wetwebmedia.com/glstksilasticf3.htm
If you don't want to follow leads from using the search tool (is on every page)... And the wider Net. Do write back if you have specific questions, concerns. BobF>
Re: Plywood Glass DIY   12/29/12

Yes, I did read here before attempting to re-silicone, and I used acetone.
<About the best...>
It was a very bad leak before hand, and afterwards I did notice a leak for a couple of days.. it was pretty disappointing.  Do you suspect I did it wrong, and that I should just try again, or should I break the tank down and redo the inside seams as well?  I really appreciate this web site by the way.  And thanks again.
<... Does the tank (originally) have a frame? Plastic? Chrome steel/nickel? Did you re-use it/this? B>
Re: Plywood Glass DIY   12/29/12
It has a plastic frame that I didn't remove.
<... I would... and all the Silastic... including twixt the panes, the joints...>
 The tank was used for a ball python, and the heat lamp warped the plastic a bit and discolored the silicone (that or old age discolored the silicone).
<All needs to be removed... see WWM re>

Re: Plywood Glass DIY    1/2/12
Happy new year to you!  So, I started taking the tank apart and the first pane of glass broke (boo!) - then I had an idea.. could I reassemble the glass I have left, and make a plywood box with holes cut out for the front and sides (with no wood in the corners except the "trim"), and make the
thing 4 inches deeper - giving me about 65 or so gallons to work with - AND I can cutout holes in the bottom of the plywood for a sump!  I understand that I'm new at this, so I may have a poor idea on my hands, I was wondering your thoughts.  Thanks!
<Ah yes. A nice project. Bob Fenner>

seal discoloration     8/13/12
bought a used tank  and have a question i have some seal discoloration  instead of seal being black in some spots its white ?
 the lady i bought it from had a real bad algae problem but brought it home and cleaned it real good and tested it for a cpl days before i set it up and no leaks.my question is is the discoloration a bad sign for the seals?
<Not necessarily, no; particularly the real seal... twixt the glass.... if this isn't discolored, no worries>
and also on 3 of the 4 corners a brownish yellow tinge to it what i need to know is the tank safe to use because its a 70 gallon tank and would be a huge mess !!!  what should I do its already setup ???
<I might try running some dilute sodium hypochlorite/bleach through the system for a day...>
  thank you for your response if you need i can send pic  thank you again be waiting for your response
<...  Send your writing through a spelling/grammar checker before sending. Bob Fenner>
twixt the glass     8/13/12

what do you mean by this ???
<Slightly archaic English on Bob's part; abbreviated form of 'betwixt', as in 'between two things'. As a native speaker of British English, I'm always pleased to see the mother tongue being maintained this way in the Colonies!
Cheers, Neale.>

R5: Larger Sized Aquarium (96x30x30) – 07/05/12
Hi Eric,
<<Hey Rick>>
The 375 gal Tank is in place on top of 3/4" Styrofoam and 1/2 Fir Plywood.
During the maneuvering of the tank, the Styrofoam at one corner got "squished" a bit (see photos).
I'm guessing there is a 1mm - 2mm gap between tank and Styrofoam (tank is empty). I'm thinking this will disappear once we start to fill the tank and the weight continues to compress the Styrofoam - welcome your thoughts on this.
<<It should be as you have surmised>>
Also, I've noticed what I believe are a few small air bubbles in one location near the top of the tank between the front and side panel - see picture (tank is 3/4" thick). Should I be concerned?
<<I don’t think so… The bubbles in the Silastic appear small as you say, and they don’t seem to “span” the seal anywhere. But… You could always move it outside and do a water-fill test (ugh!). Or if this tank is newly built (I don’t recall if you said so in our earlier exchanges), you could show the pic/get the thoughts of the manufacturer re>>
Here's a silly question, would there be any harm/benefit if I put another seam of silicone along the entire inside edges of the tank,
<<Depends… If the seal now is good/intact, no…the new Silastic will not adhere well to the existing. If the seal now is damaged then, yes…but you will have to cut away the existing seal and clean/prep the glass before applying the new coat to get maximum benefit. Bottom line… Unless there’s an obvious problem I don’t see that it would be worth the effort. But that’s your call…>>
and if there's a benefit, would be OK for me to stand inside the tank (190lbs) ... or should I put some Styrofoam pieces in to distribute my weight.
<<I see there is a bottom frame so I imagine the bottom glass sits a bit ‘proud’…as such, no, I would not get in/stand in this tank without some way to reduce pressure points/evenly distribute weight…I don’t think the Styrofoam alone would be sufficient here>>
Greatly appreciated in advance.
<<Happy to share… Do send pics when it’s up and running! EricR>>

bad siliconing job     6/22/12
Hi crew,
don't know if you remember me but i was the guy a while ago who had 4 7ft aquarium which were chipped and was asking you guys if i could use them (you said i could with a little repair), well further inspection i found that they weren't  siliconed up properly and i could only use 1 of them so i decided to resilicone up all the tanks which meant removing all the panels, cleaning them up and re siliconing them all back up.
<A big job for sure>
 well it turns out that I'm not that good at siliconing tanks together neither lol :(
<No one is good their first few goes>
I actually split 2 of the tanks in two so i have like four, 3 and half foot tanks and one of the tanks I'm using as glass baffles, overflow boxes, spare glass ect. <etc.>
Anyway siliconed all the tanks up then saw i had to redo 2 of the tanks because of bubbling , just the front panes so that was annoying.
been cured for a week now and i was getting one stood up to drill
<?! Best (by far) to drill when the panels are unassembled>
and noticed a bit of bubbling in one of the bottom corners and runs up the seam a bit which looks quite bad (see pics).
<I do>
 I was really hoping i don't have to redo another pane I'm sick of siliconing up tanks, i might actually cry (not really).
So the tanks are made from 8mm thick glass and are 90cm, 38cm, 38cm but only filling to 33cm which is roughly 112kg of weight?.
<About ten pounds per gallon finished/total weight w/ substrate et al...>
not fitted the brace bars yet or the overflow box.
<See the Net, WWM re Euro bracing>
i was thinking if i put an overflow box(8mm glass) in that corner it might take some strain off of that corner. what do you think?
thx Rob.
<With the bracing I don't think you'll have a problem here. I would use this tank as is. Bob Fenner>

RE: bad siliconing job     6/22/12
thanks bob, do you recommend a corner over box for that corner though, because i wasn't actually planning to put one there?
<Then none. B>

80 Gallon Bowfront Finish Resealing, Should I Be Concerned? – 5/26/12
Thanks in advance for your assistance with this question.
I recently purchased an 80 gallon all-glass bowfront aquarium from a neighbor who had it setup for saltwater.
Something had really chewed up the silicon corners inside, so after testing it for leaks and determining there were none, I resealed it. During the resealing I was very careful not to cut the seams and thoroughly cleaned the inside edges of old silicon with a razor blade then rubbing alcohol.
<A very good, clean job>
I used GE Silicon 1 for the job, and thought it turned out great. Now that I have the tank setup with fish, I got a closer look and there is a network of small bubbles in one area about ½ up the left hand side. The picture shows them clearly, but it doesn't reflect that they appear to be at different �levels� within the silicon.
There are currently no leaks, but I am concerned that maybe I need to take this tank apart a rebuild it. What are your thoughts?
<Not to worry... the real seal is actually only twixt the faces, joints... the bit in the corners is mainly useful for preventing folks from poking into this "real seal">
Thanks very much for your time and wisdom!
<Glad to share (what little there is!). Bob Fenner>

Re: 80 Gallon Bowfront Finish Resealing, Should I Be Concerned? – 5/26/12
Hi Bob,
<Hey Mark>
Thanks for the super fast reply!
The bubbles in the picture are actually within the edge... What you referred to as the "real seal"... Hence my concern that it may fail or worse cause a full break.
<Ahh, I do see under "auto correcting", enlarging your pic... These aren't "all that bad"... I think you'll very likely be fine>
Also, does the inside silicon add any structural strength to the "real seal", kind of like cross-bracing wood?
<Does a bit... but I really don't know how much... Many manufacturers (notably Juwel, Eheim...) don't have corner seams at all in their resale tanks>
<Welcome. BobF>

Used Glass tank - reseal?    5/19/12
I will possibly purchase a flat back hex 165 gallon
<This shape, size tank does have more than its share of seal problems...

Make sure it's set on a strong, flat, planar surface>
 used glass tank that is drilled with an overflow.
I don't see any visible signs of tank damage, and the tank is under 10 years old. It is a custom tank, so I cannot verify its origin.
Erring on the side of over-cautiousness, I wonder if I should reseal it by pulling out old seals and replacing with new ones. Does this have the potential of doing more harm than good, or is this wise?
<I'd test, use as is if it doesn't leak>
Is there any other measure you suggest that I may employ to reinforce the tank before I begin using?
<Not really; no>
Thank you!
<Welcome. Bob Fenner>
Re: Used Glass tank - reseal?  5/19/12

Thanks Bob. Based the on your first comment, I interpret that this size/shape may be subject to more pervasive structural issues.
<Yes indeed. They are>
 I will pass on this unit. As always, thanks tremendously... Dave
<Welcome. BobF>

More aquarium repair questions... Siliconing...     3/23/12
Let me start by saying that your site is amazing!!  Thank you so much for your time and efforts and especially the easy to understand and professional recommendations!
My concern is that I recently bought a second hand tank (65 gal. bow front)
with a known leak even after the previous owner had tried to repair themselves.  My intent was to reseal it myself since I inspected it prior to purchase and realized that the reason the previous reseal didn't work was because they tried only to patch the previous seal (an absolute terrible attempt at that) instead of removing the original seal and starting from scratch.  Thanks to your site recommendations, I realized this was an excellent buy if I can do this repair myself.
<You can>
Now the concerns are addressed... upon removing all of the inner silicone, some of the silicone was removed from the seams... (my help was not quite savvy on what exactly needed to be removed).  The tank is still intact but I am concerned once it is finally resealed that the structural integrity has been compromised since maybe half of the seam was removed.  Is it possible that I could use a type of liquid epoxy on the seam, allow it to seep into the seam and thoroughly dry prior to attempting the sealing process?
<No; not of use. Either you can attempt to take all panels apart, clean away the remaining Silastic, or just try re-doing the inner (corner) seams and hoping this will work>
 Do I even need to attempt this or is there a better product recommendation?
<Only the aquarium-safe Silicone>
  Maybe even just ensuring a very thorough job on the inner seal with the silicone?  I am trying to avoid the complete tear down and rebuilding of the tank.
If this is not possible, I did not find anything in your site as to steps required for full tear down and rebuild.  Can you include them if needed?
<Are discussed: http://www.wetwebmedia.com/glstksilasticf3.htm
and the linked files in the series... carefully removing frame... cutting beads, solventing...>
Thanks so much and keep up the wonderful job!
<Will do. Bob Fenner>

Silastic re-do concern 2/13/12
Hi and thanks for taking the time to look at my question. I recently purchased a 40g tank and had to reseal it. This is my first time resealing but I'm always game to get my hands a little dirty and learn something new along the way. After resealing the tank a few days ago I filled it with water to check for leaks. There aren't any by the way. That's when I notice a few air bubbles where the silicone hadn't bonded with the glass. The biggest being about a 1/2" long the rest under a 1/4". I've attached a photo and I was wondering if it would be fine if I left it.
<This should be fine. I give you a "B", "B+" for this, your first such effort>
Thanks for your time, Colton
<Welcome. Bob Fenner>

180g with questionable <sic> seems 2/9/12
I recently purchased a 180 custom built starphire tank. It is about 7 yrs old.
Upon getting it home I realized that 3 of 4 seems <seams> don't look good.
See pictures. The worst of the 3 is half the length of the seem.
<Yes; and pic 3 and 4 are too worrisome... too whited out, too much vacuolation>
It looks like the silicone has separated half the thickness of the glass. I plan on using mmentive rtv103 and rebuilding the tank.
<Mmm, I wouldn't use this product. Having read the .pdf re its intended electronic parts sealing... I'd seek out a cartridge of Silicone labeled specifically for aquarium use>
The tank measures 57"x30"x25" is made of 1/2" glass and is euro braced. How thick should the silicone be between the glass?
<As thin as practical actually... The panels need to be carefully separated, razor blades likely employed to cut away most all the current Silastic... a solvent used (see WWM re) to remove all other and any oil from hands... Get some help from someone/s w/ experience of building, re-building glass aquariums here. Not hard to do; but takes some patience and knowledge to do enjoyably. Bob Fenner>

Re: 180g with questionable seems 2/9/12
Any suggestions for black aquarium safe silicone for a 180 gallon tank?
<?... just put the string "black aquarium safe silicone" in Google... B>

Mysterious death, Hawk, un-rinsed new sand 1/20/12
So, I have had my 60 gallon drilled acrylic tank up and running with fish and corals doing fine for 5 months. I FINALLY got around to adding the sump underneath.
I poured in that sugar fine sand
<Ohh, needs to be rinsed first>
you can get at Petco (says no need to rinse)
<I disagree>

and added water to pull the volume up (obviously I added SALT water). I get the system going, and notice there are a lot of micro bubbles, which I took care of.....
So this morning (tank now using sump/refugium 20 long for about 24 hours) I noticed my pixie Hawkfish sitting in the corner, which is odd for him (OH... ( DID remove about 20 lbs of live rock, still have plenty in the tank to a QT tank for some new fish I ordered). Anyhow, the Hawkfish died about an hour ago, and I found the body of my royal gramma.... no decay as of yet at ALL. What the heck?
<Mmm, likely this loss is related to the sand addition...>
The refugium had had about 2 days to cure (silicone II).
<Mmm, should be fine>

My ammonia is 0, Nitrites, 0, and Nitrates maybe 5 to 10.
<What re pH and alkalinity? Ca and Mg? These may have been "thrown off" by rapidly/soluble parts of the new sand>
I put in SeaGel and Polyfilter.
<These as well>
ALL my corals are closed, including the Zoanthids. I have a 10 gallon that I have had up and running with the same parameters that I may put my corals in.
<Oh! These may well have been "challenged" by the new substrate, reacted chemically (allelopathy) and poisoned the Hawk>
My Picasso pair and mocha clown pairs are sort of okay, not really happy, and will eat the Mysis a little. I wonder if I should take them out and put them in another tank.
<I would move them . NOW, if you have another established system>
I just have NO CLUE... I am guessing maybe the silicone?
<Not likely the sealant. I have used it/this many times, allowing only a day or two to cure... w/ impunity>

If so, any suggestions or thoughts.
<Please do move your fishes, and read here:
for a general review of allelopathic phenomena; and here: http://www.wetwebmedia.com/envdisphysiof.htm
for some accounts of such "cascade events". Bob Fenner>
Re: Mysterious death, now asserted Silastic issue? 1/20/12

First.... Silicone must be cured for 2 weeks or it will poison the tank....
<What reference do you have for this? Again, I've used the GE, Dow-Corning products for decades and had no such problem>

Read on, that sentence is for people looking for a quick answer that maybe not want to read all of this! I know what happened. First, my ph, Alk, etc were fine, I didn't mention those since I didn't feel it was important.
I have a friend who owns oceanpro aquatics, mike has been in the biz a long time and he has built many a refugium with glass tanks and glass dividers like this one I built. After consulting with him, I believe it is the sealant.
This was not aquarium designed silicone, just from home depot.
He told me the ammonia that is released from the silicone would not register on the test since it is a different compound or type of ammonia.
I am assuming he meant not from rotting bodies but a chemical. It did have a strong smell. Now, if I had not caught the problem, then the resulting deaths would have produced the type of ammonia that would register!
<? See your statement below (now above, posted on WWM); you state the NH3/NH4OH was 0>

out of desperation I still put in a product that eliminates ammonia nitrate and nitrates, and that actually seemed to help the problem. Thend clowns looked better and started acting better. I still moved my Picasso pair and my corals to another tank that I had set up.
He said they would wait 2 weeks before using any tank that was used for a refugium. They also would rinse it 4 times. He also thought maybe the sand as well but I told him that there were absolutely no particles floating around or getting into the gills, plus that would affect the clowns in the same ways, but being damsels, well they toughed it through.
I have actually used this same sand in the past without rinsing it with no problems to an established tank.
Ammonia from the silicone caulk makes sense, since with every tank problem like this, usually it is the clown fish that survive! I have to sadly admit that I recalled another time I did the exact same thing with another tank years ago and had a few fish die before I caught it. That situation I used rinsed sand and it was not sugar fine.
Lesson is...... Do not use a freshly silicone tank unless it is 2 weeks old or it is aquarium tank silicone. I do a lot of reading and this tidbit of information was not stumbled upon! I feel like a fool for this, yet I suppose we all have made mistakes when attempting a new venture.
It kills me to admit this, but if this helps someone else from the same problem, I'm all 4 people knowing about it.
<Thank you for sharing. Will accrue. BobF>
re: Mysterious death 1/20/12

Please try reading thoroughly before putting in commentary. The ammonia WAS 0, again chemically it would not register.
<... there is no such thing as "other ammonia"
... See the net, textbooks re basic aquarium water chemistry. I taught H.S. chemistry, physics and bio...
Re: Mysterious death... Silicone? 1/20/2012

Sorry, I meant to simplify, and used an incorrect analogy. Correct, there is only one ammonia. Point was the chemical released from the uncured silicone causes death, which would not register as ammonia, would kill, which would cause ammonia from dying creatures.
<Stop this nonsense. READ the manufacturer's recommendation for using, curing their product. It's been used for decades, by myself since the late 1960's... >
I am sorry I am not a chemist and insultingly correcting me on the main point is not professional.
<... are you being charged for these corrections, input?>
You could have easily stated, "although the silicone didn't produce ammonia, the poison could have killed weaker fish, which would have lead to it if unchecked". BUT, why dis adding a product like prime help
the situation? So maybe I speculated, so reason to be rude. I put this on to warn others, against my better judgment, so next time I will not bother you with my stupidity.
<READ where you were first referred. The likelihood here is that the Zoanthids were "disturbed" period, and the "cascade event" led to poisoning of your system. B>

Aqueon 40 breeder silicone seam worries, they say it's ok!?! 1/20/12
long story short: purchased an Aqueon 40g breeder from Petco 12/26/11. i thoroughly inspected the tank from top to bottom before purchase, everything looked fine. paid for it, brought it home.
took the tank to the basement for a leak test. laid it flat on my cement floor, pulled the garden hose in, and filled it up (it's quicker that way).
No leaks at all, but immediately I noticed bubbles in the silicone.
Puzzled, i immediately blamed it on the COLD cold well water (30-40* vs. room temp of 75ish). I emptied the tank, and the bubbles went away.
<Mmm, troublesome>
purchased a marine land stand made just for a 40 breeder, sat tank on it, filled with sand and room temp RODI water...bubbles came back. Again, no leaks, and when I run my finger up the silicone on the inside of the tank, its smooth and sealed tightly to the walls.
frustrated at the appearance and potential concern of leak, i email/call Aqueon for advice. I emailed these pics to them and after their staff reviewed it, they said that the bubbles are from the curing process,
where it seems there was a humidity problem and the silicone didn't cure all the way. Being that silicone dries from the outside in, the seal was made, but left the bubbles. They said it wouldn't cause a leak, but I could return it for a refund ($40 ) or trade.
<... The last image is especially worrisome. I would trade this tank in>
Trouble is, i already had a professional glass shop drill for my Glass-Holes.com overflow/return kit, so I'd be out that cash and have to drill again. This also voided the warranty and after i mentioned it, Aqueon quickly got off the phone.
<Ohhh.... In that case I'd run a new bead of Silastic inside all internal joints. See WWM re technique, here: http://www.wetwebmedia.com/glstkreptech.htm
Please see the attached photos, and judge for yourself...are these a problem?
<Too likely so; yes>
Again, tank is not leaking, has been in its current state for almost a week (wet and running) with no issues. My quick fix is to apply electrical tape over the silicone, thus making it look like black silicone.
<Looks are not function>

Works for me, but I wish it was how it should be.
What's your opinion? Thanks!
<Welcome. Bob Fenner>


Re: Aqueon 40 breeder silicone seam worries, they say it's ok!?! 1/20/12
Thanks for your confirmation. I have taken the tank down, and Aqueon has confirmed that they will let me return the tank, even after drilling, for a full refund.
<Ah good>
I hope to be able to upgrade to the Aqueon 65g MegaFlow predrilled tank and retain the same marine land stand I have for my 40g breeder.
<Mmm, the Mega is a bit exaggerated... these have had only 1" through puts. DO check ahead... and read ScottV's piece on what flows can be expected...:
and the linked files above>
Can't tell you how many times Google has led me to your site and let me find the honest results. I appreciate your work and am glad to get in touch with you!
<Ahh! BobF>

Little Old Lady worried about old tank, glass aquarium/seals longevity 1/18/12
I hope you can point me in the right direction; I have read a lot of your excellent responses, though things like silicone are mysteries to me. In brief:
<Will do my best>
. I am an elderly woman living alone (except for lots of critters),
an academic who has no practical skills in repairing anything;
. my deceased husband gave me, about 20 years ago, an O'Dell 55-gallon aquarium plus a wooden cabinet on which it sits and a wooden hood;
<Ahh, yes... I sold O'Dell at Sears many years ago, and bought/sold the brand for Petco in the early 90's>
. the tank is a freshwater one with a few inexpensive fish and lots of plants, and I love them all;
. HOWEVER, the age of the thing just dawned on me and when I asked the young fish man at Petco about how long it could last he told a harrowing story about his family's tank cracking open and spilling the entire contents;
. I could not cope with that; just thinking about it makes me very nervous;
<I can imagine>
. A) how long could my tank still 'live'? B) do you know of anyone
I could hire in the Fairfax, Virginia area who could either reinforce it or install a new aquarium and transfer the contents of this one? I know that would be expensive, but it would be buying peace of mind!
<This tank is likely fine. Silastic (the sealer that holds the glass panes together) can be weakened by exposure... the tank left empty in cold and hot weather... But if kept away from such, it can/will last for many decades. Longer than you and I!>
Thank you very very much for any advice you can give me!
Old Professor (I'd rather my name not be used if you put this on your Web site.)
<Will not post then. Cheers good lady, Bob Fenner>
Re: Little Old Lady worried about old tank 1/18/12

Oh gosh, that's such good news--I've been worrying about what you would say since I sent my message. Thank you so much for responding so promptly (and reassuringly!)
<Certainly welcome. BobF>
God bless you!

Looks like air bubbles in glass to glass seam/joint 11/4/11
Hello my name is Mark I have been reading your site for a few months now just doing research on fish tanks, hoping to get one set up. Well I purchased a used tank from a guy I work with for $150 with stand hood and light, he Say's it is 20 years old and at least 15 years old, and has not had water in it for 5 years( tank was kept in his basement) but before that dry period, it was full and doing just fine, the tank he said is a 120 gallon. So I got it home took some measurements ( 72in L x 18in W x 25in H glass is 1/2in thick all around) its in the garage of course. The silicone seal of the tank was dry rotted like a creme color and flaky, so I resealed the tank ( first time doing this but am very handy ). Anyways waiting for the new seal to dry for a few days I had my motorcycle running getting ready for winter the headlight was pointed right at the tank and I noticed what looks like bubbles maybe, between the seam/joint of two panes of glass more so on one side than other sides but I am not real certain what they are,
<Mmm, are bubbles, "air">
it is cool here so I am giving the silicone multiple days to fully cure, so I have not filled the tank with water since I have had it. ( maybe a full week I have had the tank) I have included pictures of the problems I am speaking of. Well I certainly hope to here from you soon please and thank you sir.
<You're likely fine here... some bubbling is not dangerous. Let me make sure and ask: "This is/was done w/ aquarium Silicone for sure, right?" Not any other non-aquarium intended Silastic. Do test fill of course. Bob Fenner>

Re: Looks like air bubbles in glass to glass seam/joint 11/4/11
Hello again. The silicone I used was GE Silicone 1 100% silicone no additives or even ingredients 100% silicone. I filled the tank with water, no leaks so far but I did notice on one of the seams a line of air bubbles that were not visible with no water in the tank. I did not do a complete tear down of the tank so the silicone between glass is at least 15 years old.
<So far, so good. BobF>

leaking tank. Silicone use f' 11/1/11
WWM Crew -
I recently acquired a 65 gallon aquarium. It is basically a 55 gallon with a flat back, hexagon shape in the front. The tank is an Oceanic and is about 10-15 years old.
<A good manufacturer I'd warrant>
I filled it with water and it had no leaks, so I drained it and moved it to the position where it would be set up. When I filled it for the second time, with 45lbs of rock at the bottom this time, the silicone gave way on the top hex section on the right side from the top down. The plastic trim on the top seems to have come apart and the silicone gave way from the top to about 6" down. To say the least it was a mess. Here is my question, I want to undergo resealing the tank myself, but would like to only reseal the broken section as I do not trust myself to reseal the entire tank. Is it possible to reseal just the one vertical section?
<Mmm, yes; though better to cut away, replace all inner seams while you're at it>
I fear that the new silicone would not bond well when it meets the old silicone at the bottom.
<This is so... again best by far to trim away all (single edged razor blades), scrub residue w/ a solvent (as listed on WWM), and re-run a new continuous bead...>
In order to prevent another leak, I was considering running new silicone throughout the entire tank (very large bead) over the existing silicone in all the areas besides the broken section (this section would be scraped free of old silicone).
<Mmm, don't do this... as you've stated, the new won't adhere to the olde... and it will look... "funky"... a mess you'll be reminded of every time you look at or think of this system. Maybe have someone w/ experience show you "the ropes" w/ working Silastic... use a bead-placing tool... let cure for a day or more... trim off the excess. Not hard to do once you've been shown.>
I was ensure <unsure?> that the new bead of silicone around the entire tank meets the glass for a proper bond. Thoughts on this?
Blake Higgins
<You have mine... from many years, trials of doing this. Take your time here. Cheers, Bob Fenner>

Fish Tank Re-seal problems 10/16/11
Good Evening,
I tried to re-seal my 150g fish tank and used a lot of the methods discussed in the forum. I stripped the old silicone, used Alcohol to clean the surface, applied tape,
<Mmm, I like to just use an application tool... and trim off the excess next day with single-edged razor blades>
then started to lay the silicone. Clearly I was not good at laying a bead of silicone as even with the tape, it seemed to clop up
<This is the Silastic product, not you... the tube you used is bunk... Too olde, perhaps exposed to heat>
and somewhat made a mess. My question is this, after it cures, can I take a razor blade to clean it up or will that compromise my seal?
<As long as you don't cut into the glass to glass seal you should be fine>
Any ideas on what I can do?
<Trim it. Bob Fenner>
Thank You,

Become a Sponsor Features:
Daily FAQs FW Daily FAQs SW Pix of the Day FW Pix of the Day New On WWM
Helpful Links Hobbyist Forum Calendars Admin Index Cover Images
Featured Sponsors: