I'm off work tomorrow and going to put up the posts for my dock. I'm using 12" sonotubes under 6x6's for the footers.

After the concrete is dry should the sonotube by cut off? I know that sometimes in dry construction the tubes are sanded and painted or plastered.

Thanks,
Eric

Eric,
Whenever I worked with sonotubes, the hole I drilled was usually a little sloppy near the top from the augur wiggling. I would slip the tube into the dry hole until I felt resistance, then lean on it a little more to make sure they were vertically snug. If you need to plumb them, before you jam em in, you can use a level and tilt em a little and press dirt into the sloppy top of the hole with your foot on the side that needs it.....then press em in to secure for the pour. For aesthetics, I have even cut the tops off of some to get similar concrete pier heights, but you risk shaking your previous plumb-job loose.
Regarding "after the pour", they will eventually deteriorate...they are basically cardboard. I have not worked with a sonotube that wasn't. On my deck jobs, I let the sun and weather soften em up for a couple of years, then they peel off following the spriral seam that was used to create them. For a pond, fuggetaboutit. If it bothers you, after a couple of months of saturation, put on your swimsuit and...well...you know the rest.
As a footnote, if you are using a concrete truck for the pour, I will use a 24" cut-off of a tube and cut a strip out of it lengthwise. You can form the leftover tube as a "backstop" to guide the concrete that is shooting out the end of the truck chute and into the hole.

Good stuff, thanks Brettski. I'm not doing anything but these four 6x6's until the pond is full, so I'm digging the holes by hand with a posthole digger. I've already dug out the rough holes and was hitting quite a bit of limestone just a short way down. So the sonotubes aren't going to go down as much as is usually recommended. But they should be fine as I decided against a roof, and didn't end up getting 16' 6x6s. I'm filling the tubes by hand with bags of sackrete. When the pond fills up to "summer pool" I'll be taking a swim to finish the dock Not ready to decide on deck level yet until I see where the water level will stabilize at.

...just remember, the true application of a sonotube is to "form" the portion of the pour that has no form. If given an option to push it all the way to the bottom of the hole, or only half way, the better choice is half way and allow the the concrete bearing mass to form and bind with the subsoil below. Use a 1 x 2 firring strip, running it up and down methodically after the pour right into the concrete, to minimize air pockets and to assure a homogeneous pour; about 20 strokes up and down in varying points across the entire concrete area.
Are you going to use post anchors?

I'm not going to have the option to push the sonotube way down in the hole ... too much limestone and they aren't very deep. Planning to put the tube in most of the way with a little gravel at the bottom. I'm not using post anchors, shouldn't be any need for this application.