120G Fatboy gone off-level

[linus.chan]

Not sure what happened, but i have noticed that my tank (been set up for 2 years now) a 120Gallon fatboy is now a little off-level. How much? 1/4" over 4' so about 1/16" over 1 foot.

This is obviously concerning. My tank rests on a rubber mat, on top of cork flooring in my basement. I had shimmed the tank when it first was filled, but not sure if over the years the shims (wooden ones) lost their efficacy.

How concerned should i be? Should try and re-shim the tank? Should i shim even if i don't get the full 1/4" back?
There is no other indication of stress or strain in the tank, but obviously i am not sure anything would show before something disastrous.

I am using a DIY wooden stand.

 

[linus.chan]

bump

 

[Bao]

1/4" is a lot for 120 gallons of water. You might want to make sure the floor can support that much weight.
The only thing that I can think of that would make your tank uneven after 2 years is that the floor is sinking on 1 side.
When I setup my 120, I spent quite a bit of money to support the floor

 

[Greybeard]

Cork flooring in a basement, I'm assuming that's a concrete floor under the cork, right?

Concrete basement floors don't generally settle much, and if it does, it's usually easy to tell... what with the cracks and all Cork will compress, but i'd expect it to do that fairly rapidly, and hopefully by an even amount. Same with the rubber mat.

I'd guess your DIY wood stand has warped, shrunk, or settled a bit. Alternatively, the cork/rubber under the original shims may have compressed more than under the surrounding even load.

I'd probably drain the water, re-shim, and re-fill. A couple rubbermaid trash cans or whatever, siphon out 80% of the water or so, just leave enough for the fish to remain upright... re-level, and pump the water back in. Do it fast enough, it shouldn't hurt the reef.

That said, I've had several tanks that were 1/4" off end to end the day they were set up. Never really bothered me, and didn't hurt anything.

 

[Rip Van Winkle]

Cork flooring in a basement, I'm assuming that's a concrete floor under the cork, right?

Concrete basement floors don't generally settle much, and if it does, it's usually easy to tell... what with the cracks and all Cork will compress, but i'd expect it to do that fairly rapidly, and hopefully by an even amount. Same with the rubber mat.

I'd guess your DIY wood stand has warped, shrunk, or settled a bit. Alternatively, the cork/rubber under the original shims may have compressed more than under the surrounding even load.

I'd probably drain the water, re-shim, and re-fill. A couple rubbermaid trash cans or whatever, siphon out 80% of the water or so, just leave enough for the fish to remain upright... re-level, and pump the water back in. Do it fast enough, it shouldn't hurt the reef.

Agreed.

I think you should take advantage of the fact that it hasn't leaked yet and make preparations for your tank's inhabitants to be temporarily relocated/moved while you fix the leveling issue.

About 3 years ago I got a call from a friend asking me to go over to his place and help with his 120g that was leaking, because he was at work at the time. The edges where the silicone makes the seal between two panes of glass in the corner on one end, had started to separate from each other. When I got there, his family members already had buckets under the tank to catch the water shooting out like a fountain. Aside from that, his particular tank was not euro-braced and I really thought that the tank might actually burst apart. When that much water starts to leak, it's not pretty. I wouldn't wait if I were you. Just sayin'.

 

[AlexG]

My first concern would be is how the tank has changed its position to become out of level. If the tank has once side a 1/4 inch off without twisting the tank it should be corrected but it should not be putting extra stress on the tank seams. If there is twisting action on the tank due to the level change it will stress the tank seams and ultimately cause a failure of the tank seam. The level readings should be taken front to back, side to side, and diagonally across the corners of the tank. This will help to determine if there is a twisting action on the tank. If there is a twisting action taking place on the tank seams get it fixed as soon as you can. For leveling the tank I would remove 50-75% of the water which should allow new shims to be placed under the tank.

 

[linus.chan]

Thanks AlexG. So i have had to think back and i am wondering whether it has been off level from the start. When i originally leveled the tank, i did so dry and thought that i had leveled it. To give context, when i use my level, the "bubble" stays within the two hash marks- and still does. The bubble just favors one side a bit more. I didn't even realize it was off level until i took the canopy off and noticed that the water level on one side was higher than the other side.

Now as to the twisting action, i will need to check again, but i do believe it is level from front to back.

Assuming i am going to "re-level" the tank, what do i do with the old shims? I have wooden shims already underneath. (one reason it may have drifted off level is that these shims would get wet when i spilled water- and usually i only spilled on one side of the tank). I would be using composite shims.

When i re-shim, should I also try and take out the old shims? IF so- how is that done really? My main concern is adding stress to the tank by trying to re-level it, even if am able to empty 50-75% of the tank that is still a lot of weight.

 

[linus.chan]

AlexG- what i the best way to take a diagonal level measurement? My level will not go from corner to corner, should i just go off angle?

 

[AlexG]

Thanks AlexG. So i have had to think back and i am wondering whether it has been off level from the start. When i originally leveled the tank, i did so dry and thought that i had leveled it. To give context, when i use my level, the "bubble" stays within the two hash marks- and still does. The bubble just favors one side a bit more. I didn't even realize it was off level until i took the canopy off and noticed that the water level on one side was higher than the other side.

Now as to the twisting action, i will need to check again, but i do believe it is level from front to back.

Assuming i am going to "re-level" the tank, what do i do with the old shims? I have wooden shims already underneath. (one reason it may have drifted off level is that these shims would get wet when i spilled water- and usually i only spilled on one side of the tank). I would be using composite shims.

When i re-shim, should I also try and take out the old shims? IF so- how is that done really? My main concern is adding stress to the tank by trying to re-level it, even if am able to empty 50-75% of the tank that is still a lot of weight.

If you are using wood shims and they show signs of being wet I would remove them and get some composite shims. Home Depot, Menard's, & Lowe's all carry these composite shims which are made of wood and plastic or just plastic. The composite shims are easy to work with and are not impacted by water. Moving the tank to re-level is not always easy and I would recommend having a one or two helping hands. The tank must be gently leaned without twisting the tank (or letting it slide off the stand) in a way to allow for new or additional shims to be added. Most tanks are top heavy on the stand so they can leaned on the long side of the tank enough for shims without a significant amount of force. If you still have concerns on weight or stress on the tank seams I would remove more water and/or rock. The lower the water level is the less stress will be on the aquarium seams. If your level cant reach the entire span get as close as you can and crisscross the top of the tank with level measurements. The diagonals should all measure the same reading if the tank is not twisting even if one side of the tank is off level front to back or side to side. Diagonals in your case will be off level but they should all be equally off level if there is no twisting action. (Note ensure the top of the tank is level and any bracing on the top of the tank does not have imperfections that might throw off the level measurements). I would also double check that the bottom of the tank and stand are contacting around the entire perimeter of tank without any gaps as that can also create stress on the tank that can cause a seam failure.

 

[linus.chan]

If there is no twisting- would you still recommend reshimming? So i would remove the wooden shims and reshim it then?

 

[AlexG]

If there is no twisting- would you still recommend reshimming? So i would remove the wooden shims and reshim it then?

As a general guideline with glass or acrylic tanks yes I would get the tank level if its possible. I have kept tanks that were not perfectly level before either front to back or side to side without an issue but in those instances there was no twisting and I understood exactly why the tank was slightly off level and I accepted the risk of knowing it could become an issue down the road. Since you have shims that could be deteriorating or flooring that could be compressing due to the weight of the tank I would put new shims under the tank to get it back to level and then monitor it every couple of months to see if if moves out of level again. I would also inspect the stand to make sure everything looks secure.

 

[linus.chan]

last question-(or so i hope) my previous shims were between the stand and the rubber mat- i assume when i re-shim it, i should do the same? And is it correct that i should really only be shimming the corners (i.e. not the rails under the stand). i made that mistake the first time around in terms of leveling the stand.

 

[AlexG]

last question-(or so i hope) my previous shims were between the stand and the rubber mat- i assume when i re-shim it, i should do the same? And is it correct that i should really only be shimming the corners (i.e. not the rails under the stand). i made that mistake the first time around in terms of leveling the stand.

If it is a soft rubber mat that compresses I would leave it out. If it is a hard rubber mat it can stay in. The shims primary location should be the corners but if there are additional supporting legs on the stand in the rear or front they should also have shims under them. Rails don't need shims but they can be placed in lightly until they are snug as long as they don't interfere with the shims under the supporting legs of the stand.