Paul, great post, and fun projects thrown in.
I just put a Diatom filter together, to clear up the water, very basic so far, and put it in service, I will clean up the package after I refine how to make it easy to use. I ended up starting unit in tank in a bucket.
I have now read all 13 pages of this post and see that you have gone through multiple iterations of the unit.
I saw that you attempted to place a down tube in the filter to disperse the Diatom but found there was not enough room
I am running the filter under pressure rather than pulling water through.
I am thinking that I would run the filter upside down, so that the incoming flow would mix the Diatom, in hopes of making startup easier.
Is this something you have tried or have a reason not to try?
I am very surprised these are not readily available, they are very simple. No one has posted anything negative about the concept, is there any downside, does it possibly strip out good things in the water. Should it not be used for long periods of time? Heck , your 50 year tank makes me believe you are pretty good at reefing. I am 6 months in.