Need advice on cracked fishtank

  • #1

I need some advice on how to repair a cracked pane on my 36" 15" 18" tank.
I have had a bad weekend, As I had just finished my tank and all the fish where happily in my new tank
when we noticed a complete crack had formed on one of the sides of my tank.. the tank was brought second hand and was checked all over when I started to build my own cabinet and hood..

so my question is will I be able to replace the cracked side with a thick peace of perspex or use it to repair it...??
the side is not viewable as it is built in to the cabinet so will not be noticeable from the outside..

please can anyone give me some advice or if they have used perspex on there own tank... thanks lee
  • #2
Timg would be the man to be able to help you here, as he builds all his own tanks and has done such a great job. I hope he finds your thread. IMO a cracked tank has compromised the strength and on your size tank it wouldn't be a good idea to try to repair it unless you took the whole pane out an redid it. You would have to remove everything tho. Good luck!
  • Thread Starter
  • #3
thanks capekate
I would prefer to replace the panel as I want to keep the tank for a long time..
and I have spent a lot of time in building this tank up and makeing the cabinet..

I don't know where to buy a peace of glass from the size I want, so I have read somewhere that you can use acrylic perspex to build a fish tank and use glass for the front, so as you can't see my fish tank sides I thought I would be able to use this to replace the broken side... anymore advice would be great..???
  • #4
I have replied to your mail, but just read the thread. To remove the broken side panel is very hazardous and likely to cost you the whole tank, so I would suggest you repair instead. The only time I tried to cut a broken panel off a tank, I ended up having to replace three panels! The silicon used in the manufacture of tanks is very tough and any leverage you use will compromise other panels. I have sent suggestions in the mail, but here is a summary of the contents for others to comment on:

Option 1. To cut a piece of glass or perspex to the overall size of the side panel and secure with silicon on the outside of the damaged panel. (Subject to leaks and risks failure due to the outward pressure of the water on the damaged panel.) You could end up with two broken panels, not one!

option 2. To measure the inside dimensions of the damaged panel and cut the new panel 5mm smaller, so that it will fit inside the tank without disturbing the existing beads and seal around the edges. More stable and much stronger, unlikely to fail or leak. Water pressure is against the new panel, not the damaged one and the existing silicon corner beads continue to take the strain without being disturbed.

Glass vs Perspex: My preference is for glass, as perspex has a problem with adhesion to silicon. Modern acrylic tanks are formed in a single unit with no joints and therefore no need for silicon. If joints are needed, they use a special silicon/glue combination, which I have been unable to duplicate. If the silicon does not adhere to any of the joins, failure is imminent, and this could be very stressful as well as wasting time and money. Find a glass supplier and make the job permanent.
  • #5
Your repair ideas sound good, but I wanted to comment on your statement about the construction of acrylic tanks. From what I have seen and heard, they don't use silicon or glue. They use a cement that melts the acrylic for a little bit. The melted acrylic then fuses at the edges. For larger areas, they make a glue out of acrylic and the cement, creating a liquid acrylic goop.
The method needed to bind acrylic makes it nearly impossible to mix acrylic and glass in construction. Since glass doesn't melt in the acrylic cement, and since acrylic doesn't bind to silicon or glue, the two are very hard to stick together.
One note. If you are going to use acrylic to fix the tank, make sure it is cell cast, not extruded. And you're going to want a piece at least 1/8 inch thick, if not 1/4. Cell cast is far stronger than extruded. Extruded apparently tends to bow in tanks taller than 12 inches.
  • Thread Starter
  • #6
Thanks for all the advice..
I have read lots of ideas on other sites about different materials to use on fishtanks and I have decided not to use arcylic on repairing my fish tank as I don't want the risk of any more leaks.. ive also found out that I can pickup another tank with extra parts n filters for around 50 pounds.. so I will buy a replacment and leave the old tank.
but after looking at different sites on building fishtanks with the use of acrylic panels, it has given me a idea to try and build my own tank some day or when I have some spare time..

To further the debate on acrylic vs glass I have found a great site to way up the differences and to decide what is best to use on building a tank..

thankyou for your all your advice..
  • #7
You're welcome and thanks for the input sirdarksol. I have tried various methods to join the two, all have failed and even tried the cement that you mentioned to no avail. Most of the perspex you can get in diy shops is extruded, which further adds to the problems and in my mail to pontiac, I recommended at least 12mm anyway, to be on the safe side.

Sounds like a good deal on the tank pontiac, but don't write off the old one, hust keep it to one side and repair when you can. As for the idea of building acrylic tanks, I would advise against it unless you are sure that you can get the right materials and adhesives. I can't around here and find glass by far the easiest option.

BTW, the article on acrylic tanks is very informative and supports our reasoning to a great extent.
  • #8
I'm with timg on the idea of not building your own acrylic a point.
I do plan on custom-building an acrylic tank, but the parts cost far more than the websites on building your own tanks suggest. (You probably went to the same ones I did, Pontiac). After shopping around, I've found that doubling the amounts they give on the DIY websites will give you a more accurate total. This means that it becomes pretty pointless until I want a large, custom-built tank.
When I can afford it, I'll make a smaller tank for practice, then move on to the large one.
  • Thread Starter
  • #9
I do agree with both your coments..
and the price of acrylic is a lot more then glass I know, but EBAY have some good deals which they cut to size for you at no extra cost and the cement is around ?2.99 and is all shipped to your door..
so when ive finished my current projects I will definitly have a go at building an arcylic tank just to try and see how it turns out..
but at the moment I am going to shop around and find a good glass dealer so I can fix my old tank..
and also buy a replacment tank to use for now..
thanks for your help and will post how I get on with my repairs and new tank..
  • #10
Yeah, ebay is the best place I've found yet for acrylic. You can get it cheap on there, usually. The major issue is finding it thick enough to be of use.

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