I was working from home yesterday and just about to start a business call when I heard the sound of running water coming from my lounge. Alarm bells sounded and I ran in to discover water spraying out the bottom of my beautiful new Juwel Vision 450. I only set it up about a month ago.

Over the following hour I drained the tank, moved the fish, water and filters into my spare 300L which had only gone on Ebay the day before and thankfully hadn't sold. I spent a further 90 minutes mopping the floor.

Sadly I knew my floor was uneven, the people who did the floor didn't think to use concrete leveller. It drops 2 cm in each direction from the wall. I spent a good hour with a 1m spirit level propping all of the cabinet's feet at an even height using non-compressing plastic spacers of different size combinations for the perfect fit, checking and double checking, just as I did with the previous tank which ran for 8 months. Having emptied the remaining water and got the tank into the garden to get a good look at it, there's a nice long crack across the bottom, a quarter of the way from the corner at the back, spreading to the near side. One of the back feet must have been a bit lower or higher than the rest, though when I recall doing it, I can't fault my evaluation of each foot at the time, there were no visible gaps and each one was firmly planted. I'm absolutely gutted.

Thankfully my fish are fine for now, albeit in the smaller tank and the largest is looking a bit moody (ammonia and nitrite are 0), hopefully not injured when netted and moved. I bought the 450 as I'm a bit over-crowded long term thanks to rescues and breeding though about half are 2-3 inches and they're all coldwater fancies under 2 years old. On the downside, most of my house has wooden flooring, so I only have one spot to house a large tank permanently and there aren't many second hand 450s or greater about locally.

For some part, this is a tale of woe for the sympathy of my Internet fish friends and in part a cautionary tale for others: make sure any tank of reasonable weight is on a flat, level floor before you fill it.

The remaining part is to ask for advice on where I go from here. Are cracks of that nature repairable? I doubt it, since the structural integrity will always be compromised.

Can the bottom be replaced by someone with the expertise and materials? I guess so, but I Googled for such a person earlier and only found information on repairing trivial leaks. Anybody know of someone or a suitable Google search term?

Levelling my floor permanently is a big job, not least because there's nowhere to store the tank and sofas while it's done other than the garden and the weather is just starting to turn. Do people here have any wisdom with regards to suitable non-permanent under-tank floor levelling, or did I already do the right thing, though perhaps not perfectly?

The most depressing option of course, is perhaps my house with it's shoddy flooring and its awkward layout are perhaps not suitable for a large tank, which means I need to re-home and sell my tank, at least until I can get my floor sorted out.

Advice and commiserations welcome :(

You have my commiserations Poor you, it must have been awful.

You may be able to have the tank repaired if you look for a custom tank maker locally and ask nicely. It won't be cheap though as it will need the entire bottom replacing. Alternatively, if the rest of the tank is sound you could see a glazier and ask them to cut you a piece to fit inside the bottom and fit it yourself if you feel confident. You could fit that over the broken existing bottom and silicone in place.

Regarding leveling: the safest way is to get a sheet of 3/4 inch thick marine ply slightly larger than the tank and start by leveling that with shims. When it's perfectly level, stand the tank on top.

Hope that helps.

Thanks for the sympathy :) As it happens I may have just fluked across a tank exactly the same as mine on for less than I paid for mine and probably less than a repair.

And that's great advice regarding the marine ply, thank you, I wish I'd known that before.

Fingers crossed on the other tank, normal service will be resumed sooner than I could have expected.

What an awful thing to have happen :( we've just finished levelling and laying a wooden dining room floor where my 210 litre tank is to go and my worst nightmare is that it would leak all over the floor. We got self levelling mix from wickes, don't think it cost too much money, was fairly easy to lay, dried in six hours and the floor is pretty even across now, maybe a 3 to 5mm difference across the whole floor. Off the top of my head I think the dining room is 5m square - ish - and we used seven bags at about 20 quid each and it was drastically wonky when we started - up to a cm or more in some places, and wobbly, big lump in the middle, so it took more mix than normal. Though it does self level to a degree, we did have to use a straight edge just to evenly distribute it. Don't know if thats something you might want to consider, just wanted to say it wasn't as bad as I thought it was going to be!

Just to update, I was wrong about it being a crack. After leaving it to dry outside for a few days, I hosed it down to remove any remaining debris and it wasn't a crack at all. What I saw must have been a waterline from the condensation underneath.

I ordered a large piece of marine plywood for future use and used it to sit the tank on outside, put newspaper underneath the tank and filled it with water. Before it was a quarter full I noticed a 2 foot stretch where there back panel met the base with beads of water forming on the seal. Before long the paper was pretty wet along the back. No water anywhere else.

LFS advised that seals can fail when a tank has been in use, then left empty for some time, then filled again. Filling causes the tank structure to push out, leaving empty for some time allows it to contract back inwards, then filling causes it to push outwards again causing the failure. This seems to have been the case with mine as it took night on 3 months from draining to filling while I researched, shopped for bits and planned. I was pretty confident I'd been accurate when propping the tank evenly, though it's still possible that maybe some props at the back weren't quite right. In any case, if I can repair the seals I should be good as new and can use the marine plywood to give a more solid base.

In any case, since the glass itself is ok, I have a tube Gold Label "One Shot" sealant, the strongest silicone aquarium sealant my LFS sell. It's black, like the existing sealant.

Thing is, I'm not that confident about doing it myself. Does anyone know any reputable repairers around or have any wisdom to impart on actually doing the job myself? I've read a few articles on doing repairs but they tend to focus on smaller tanks. I imagine minor details on small repairs are far more significant on tanks for this size.

Thanks Emma, that does indeed give me hope. As the lounge and kitchen are a single concrete floor (and the only floor in the house which can support a large tank!), I can empty both rooms, put my babies in a few large storage boxes with filters, level the floor, lay new flooring before moving everyone into their tank. I'm thinking out loud here, can you tell?

Anyway, just an update. Hopefully my babies will be swimming in their large tank again in the next month or two.

I've redone the internal seals on tanks including my 5ft and the best advice I can offer on that is that you must clean away all the old internal silicone seal completely so there isn't even a tiny spot left before applying the new stuff. It will mean removing the entire internal seal on the leaky panel, but without cutting into the silicone between the panes that holds the panel in place as you can't put new silicone over old; it won't stick.

If it's so bad that you need to actually remove and refit the back pane, get a pro as it will have to be held in place very accurately while the silicone dries. If it's siliconed back in place with even a minor shift in angle you run the risk of it leaking again, or worse, bursting completely and suddenly.

Thanks Fishlady. If I understand correctly, you recommend leaving the silicone alone between the two panes and just resealing the part visible inside?

Some of the articles I read recommend pushing out the back pane as best as possible and removing as much as possible from between them. On a large tank with thick glass, I did think that would be pretty difficult.

The sealant between the panes on my tank obviously leaks, but I wouldn't think it is integral to the quality of seal itself, so long as the part inside the tank, between the water and where the panes meet is watertight. Do you think I'm right?

There is also some sealant where the panes meet on the outside too, I had planned to remove that, clean it up and seal there too.

At the very least, I can test whether the seal is strong enough by filling it and leaving it outside for a few weeks. If it's not, then I think I'll call in an expert. I just have to fine one!

Thanks again for your advice. You people here are invaluable.

Oh Eeyore your post has sent a shiver down my spine, the 210l tank I've got was filled for a few months and has now been sitting empty for about a year, and now I'm c**ping myself about filling it again :( I wonder how common it is for the seals to go.....the trouble we've had with this floor, it would be beyond a disaster if it got b*ggered up by a leaky tank.....can't be that common or second hand tanks wouldn't be so popular....ooh mind running riot!!!!

Haha sorry :) As it happens I've had five second hand tanks and only had this problem with one of them, which just happens to be the largest one.

It's possible that the LFS (or myself) were over-stating the case, but since yours is in the garage I guess you could fill it with a hose and leave it until you're ready to use it again. At least you'd know it was water-tight and it would keep the structure as it would be when in use. If it were to leak, then it's only going to leak in the garage which is presumably a concrete, ground-level floor and you can sweep the water out without destroying your newly levelled flooring :)

Silly fish give us all heart attacks :)

what part of staffs are you from? anywhere near dudley? as there is a glass man/fish shop owner there that may be able to help