Thanks esshup for the response and welcome....very helpful. Below are answers to your very good questions. I would like to post pics of the old and new manifold, as well as the dock I am deicing, but can't figure out how to post pic's ... just links to pics. If there is a way to do that, please let me know?

1) The old manifold is small, very small, I couldn't file clamps small enough to work. Even if I could the connections are so close together I don't think it would work.
2) I used 1/8" fitting because that's what is required coming out of the pump. I suppose I could have gone 1/8" to 1/4" right out of the pump instead of transitioning out of the manifold itself which is built with 1/8" Tee's connected by 1/8"x1/8" hex nipples. Do you think transitioning from 1/8" to 1/4" out of the pump vs. how I did it would help?
3) Yes indeed I am using plumbing tape on all threads that make up the manifold. I will check and make sure none are plugged.
4) Yes the air stones are the same as I've used for 3 years now .... without cleaning ever. I will clean them in muriatic acid.

I will make all 9 of the tube runs the same length. If I do that the total length will be 144' of tubing. Do you think the pump is "big" enough to handle that? I can make all the stones the same depth if they are 1' below (given current lake level - we are in a drought in Maine) the surface of the water. Do you think that depth is deep enough for deicing?

Thanks again, I appreciate it.