Project - Re-Sealing Fish Tank (Image Heavy)

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I picked up a large (4.5 foot wide, 2 foot high, 1.5 foot deep) second hand fish tank a couple of days ago for next to nothing & upon getting it home & removing all the packing found that it was filthy & the previous owner had done a rubbish job of re-sealing it at some point:











I decided that as well as cleaing the tank I was going to have to re-seal it properly with new silicone as I didnt want to come home from work and find 300 litres of water on the front room floor. I then started ringing around trying to find silicone suitable for this (it needs to be 100% pure silicone as any additives like anti-fungal can kill the fish). I found a few pet shops with aquarium grade silicone, but speaking to all of the maufacturer's of these products they all said it was not suitable for a tank of this size. I eventually found a company online that make custom tanks & bought a few tubes of silicone off them which they use for tanks upto 14 foot long so it will cope with my tank.

The original plan was to take the whole thing apart to 5 individual panels, give it a good clean and then put it back together. Having looked at it in more detail while cleaning & sorting the top brace out I think the silicone holding the side panels together is alright & I just need to re-do the inside seal, but the base will definitely need to come off and be re-attached as there is movement if I push the back panel. I will add black plastic edge braces all the way round (probably inside & out) just to be sure it is strong enough.

After about 6 hours of working on it yesterday with a lot of scraping & scrubbing I have managed to get it to start looking reasonable:









Todays job is to get it outside so that I can cut the base off, give it a good wash down, remove all of the silicone from the internal corners, and re-attach the base if there is time.
 
I finally got the bottom off the tank after about 2.5 hours. I was first trying to cut around it while the tank was the right way round, but the weight of the glass was making it to difficult & I was breaking a lot of razor blades so I got the tank outside & put it upside down:



I first cut the silicone holding the base & sides with razor blades a number of times until I was all the way through and then using a stanley knife. It was all going well until I got to 2 very difficult sections at the top left and bottom right corners in the image above. These sections had very little space between the base glass & sides, & I could not run the razor blades between the glass here. The blades kept bleaking every couple of mm & I kept slicing my fingers open so cue a lot of swearing.



I had to turn the tank on its side & from the inside start wedging razor blades between the pieces of glass to start lifting the base off and then push them through to the other side to cut all the way through.



Eventually got all the way through & turned the tank back upside down to remove the base (have used up about 40 razor blades getting the base off):





So job for the rest of the evening is to carry on cleaning the tank and get it ready to stick the base back on tomorrow when the silicone turns up (royal mail is **** round here & are not even capable of getting a special delivery package to me on time).

I will then need to source some black or clear acrylic corner braces as the ones I was going to get are PVC and that will apparently start the release an oily sort of liquide after a while and come away from the silicone.
 
I am going to be putting cold water fish in the tank so wasn't planning on painting it. Currently have a 7 inch goldfish that is way to large for its 60 litre tank so was going to move it over once the tank is ready and then see what my options are for other cold water fish to add.

I did last night suggest to the wife & son that we should give the goldfish away and get a lizard instead but that really didn't go down well.
 
I may be wrong but with silicone I believed the depth of the tank is the issue and the length and depth were of no issue. Its to do with the depth of the water just the same as if you dive 10 meters down in the sea the pressure is identicle to 10 meters down in a diving pool.
Any fishtank silicone should be able to fix that tank thats "proper" fish tank sealant. I believe when I bought some 10 years or so ago it was 18" certified as the vast majority of tanks are 18" or less in depth.
 
Yeh thats parcel tape round it, though the tape I used isn't that sticky so it shouldn't leave much residue & what it does leave can be scraped off quickly with a razor blade. Getting the silicone off on the other hand it a lot more effort as I am avoiding using any chemicals so have to do the following:

1. Scrape silicone off with stanley knife blade to remove most of it
2. Scrape again with razor blade to get most of the rest off
3. Rub gently with rough side of a washing up sponge
4. Rub with kitchen roll which seems to get most of the little remaining silicone to come off the glass in rolls
5. Wipe down with sponge to remove all loose biths on glass & see what is left
6. Use razor blade to detail clean any remaining tiny bits of silicone wiping down with sponge & kitchen roll as I go.

I have got nearly all of the main part of the tank done so will post some more pics in the morning, then need to clean the base up while I wait for the new silicone to be delivered.
 
robskinner said:
I may be wrong but with silicone I believed the depth of the tank is the issue and the length and depth were of no issue. Its to do with the depth of the water just the same as if you dive 10 meters down in the sea the pressure is identicle to 10 meters down in a diving pool.
Any fishtank silicone should be able to fix that tank thats "proper" fish tank sealant. I believe when I bought some 10 years or so ago it was 18" certified as the vast majority of tanks are 18" or less in depth.
Click to expand...

The problem I was finding with most manufacturers I called was that their silicone would not be strong enough for seals at the base of the tank due to its size as the weight of water will be 300kg. 1 of the companies even had a 10 year guarantee on their product that was for resticking & resealing tanks, but they said there was no chance it would cope with a tank that size.
 
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Someone said:
Yeh thats parcel tape round it, though the tape I used isn't that sticky so it shouldn't leave much residue & what it does leave can be scraped off quickly with a razor blade.
Click to expand...

phew! The sticky fresh parcel tape with glass will always leave residue and impossible to get off. As you stated if it's not that sticky you may be OK. Ergh! It's bloody horrible stuff when it's sticky mad.
 
Scraping along the glass makes the blades blunt very quickly. I got through 4 Stanley blades just doing the top & I got 100 razor blades for under a fiver a couple of months ago for my cut throat so have loads but have got through more than half of them already.
 
Yesterday I finished cleaning the inside of the tank as well as the base:





Base before:



After:



Royal mail finaly delivered the silicone & I managed to find a local company that would cut acrylic lenghts for a reasonable price & quickly. I didn't get molded corners as the cost was to high (£160 + VAT for inside & out due to size) & would have taken almost a week to get made up and delivered. I also didnt get black acrylic for the outside as I could only find it with a gloss finish which I didn't want and it was a lot more than the clear. The clean strips for the inside were £40 cut to size, the black would have been £95.



This is the silicone being used which was £4.50 a tube so not a bad price:



I then taped everything up ready to seal:







I attached the base, taped it up, turned it over and started sealing the inside & attaching the acrylic in the corners. I started by using a knife with a rounded end to smooth the silicone, but that was not giving a great finish, I then tried a tea spoon, but again that was not great, so I used my finger which was doing a good job, but I soon found out that the edges of the acrylic were razor sharp and slicing my fingers open:



After slicing the ends of most of my fingers open I decided that I would have to cover the whole of the acrylic in a thin layer of silicone so that any fish didnt cut themselves if they scraped across them. This and the fact that it had got dark, so I was using a torch to see what I was doing, has made the finish of the silicone look a little rough and messy in places. None of it will be visible for the outside so that doesnt bother me to much, as long as it is water tight. I am now going the leave it until tomorrow evening at the earliest before giving it a wash out and then filling to leak test.

The camera bettery has died, so will get some pics of the inside once I find the charger.
 
I got here too late to suggest a Fugi kit :( sorry. Great tools for applying silicone and getting a brilliant finish.

Looking great though! Apart from the thumb.
 
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