Tank leveling issues with tank that has out of level rim

[ChrisNH]

The question: Is it reasonable to use the distance from the bottom glass to the top of the water level as my "level" given the top rim (and/or bottom rim) is not even?

I have been going nuts trying to get my 40B "standard" tank level on my DIY (Using RocketEngineer plans) stand. The tank is not new, I picked it up with a sump from another reefer 10 years ago and never got it put together. My stand was level before I started to level the tank and it was sanded to a level plane. It sits in a 2'x3' sump tray in the basement so the usual shim method can't really be used. I figure out what I need, drain the tank, tilt the stand, and add the appropriate shimming. To make things fun, the basement floor is not really level nor even a plane.

This seemed to work when I had the tank backwards so I could work on the rear plumbing. I added a 1/8" strip under one side to fix the level over the length and a few composite shims in one corner fix the front to back level. Visually the water line seemed in line with the top rim. Huzzah!

When I rotated the tank after doing the rear plumbing it appeared to me dramatically out of level. Boo.

What I discovered is that the top rim is actually lifted 1/8" in one corner. I determined this by measuring between the bottom rim and the top rim. There is a 1/8" difference. So.. now.. when you add the 1/8" lift with the shim I used to account for it before, it visually appears to be 1/4" out. Weirdly, the bottom rim is perfectly level on all three reachable sides. Maybe the bottom trim is off?

TLDR: Tank trim not useful for leveling, need other method.

What I am left with:

Left to right:
Stand: out of level 1/8" high (the height of the shim under it)
Top rim out of level from bottom trim, 1/8" difference in "window" height left to right.
Bottom rim - currently perfectly level - may also be out of level since I know the stand is shimmed "up" one side.
Glass on bottom to water level - currently 1/8" too low on one side.

Front to back: less than 1/16", will keep current shimming in the one corner that had been dipping a little. It is "close enuff".

Q: Is it reasonable to use the distance from the bottom glass to the top of the water level as my "level" given the above? I expect if i remove the original strip of shim material I will still be < 1/16" off but I consider that good enough for a rimmed tank like this.

Thanks for your help.

 

[tsouth]

What if you placed the level inside the tank on the bottom glass. What does it look like in there? I would think that is the most important.

 

[ChrisNH]

What if you placed the level inside the tank on the bottom glass. What does it look like in there?

My 4' level won't fit in the tank of course. My 8" level shows it level, sloping by the width of a piece of paper. I think it's good but I plan to go out today and get a 24" level and check again. I need a mid-size level anyway.

 

[tsouth]

My 4' level won't fit in the tank of course. My 8" level shows it level, sloping by the width of a piece of paper. I think it's good but I plan to go out today and get a 24" level and check again. I need a mid-size level anyway.

Let me ask you this - When all is said and done, would a new 40B put you at ease? With the tank being 10 years old, I think you deserve the peace of mind of a new one right now, and moving forwards.

 

[ChrisNH]

That would fix a scratch it has near the top too but given I have already drilled and painted this one I am not excited about buying a new tank until its time to upgrade to something tang compatible. Plus, I somewhat sold this to the wife as "how about I get that tank going I have had sitting around for 10 years.."

I think I am comfortable with this one as long as I am not given any reasons why leveling the bottom glass is not a valid strategy. I do know that guy before had success with it (picked it up through a local reef club, was not a craig's list dump). Good question though and I considered it.

 

[MTBake]

Agree with above. Level the bottom glass. Then double check the sides vertically just for a double check. The plastic trim on top can vary as it may or may not be fully seated.

 

[x2uranium]

Yep also it’s a 40gal doesn’t really need to be perfectly level on a tank that small

 

[ChrisNH]

Then double check the sides vertically just for a double check.

It had not occurred to me to check the sides. There is a simlar "paper width" lean consistent with what I see on the bottom. I don't think i could correct that even if I wanted to.