tank leveling problem?

So we set up my friend's tank last night and it was level every way we checked it. Filled it with water and I noticed that right when the water started going into the overflows, one overflow was filling up and the other wasn't. The one overflow filled up about half way before water started falling into the other overflow(they are on the corners). So it seems the tank isn't level. But we checked it again multiple times with a level on the tank and stand and it is perfect. Should we shim the one side anyway to try and get the water level? Or am I missing something here?

 

do your overflows have adjustable "slides" inside to adjust the rate that water flows into them? If they do, adjust them until the water level is even in both.

 

No they are just the standard AGA fixed overflow boxes. I thought maybe one box was higher than the other or had different slots cut out but they seem to be identical. So the only explanation I have is that the tank is tilted a hair to one side.

 

That is very possible since the plastic edging can be glued on uneven.

 

True. You could shim it a bit or file the teeth a bit.

 

it worries me, doesn't seem to bother my friend but it is a big tank and hate to see it blow out. I really don't think it would but man I know when I set mine up it took an hour to make sure it was perfectly level

 

I agree with being carefull. An hour now beats hours later.