I drilled 2 holes in the ends and stuck 1/4" dowels through. From these, I can hang filter media bags with coins within. I put roughly 40 coins in each bag, and can easily hang 10 bags on the dowels. Filter media bags are nylon? bags with a very fine mesh, which should facilitate water movement.
I am currently still using two air stones and the old style filter with the deionization resin.
I have added one of the newer types of filters... that looks like a waterfall in operation.
I cut a hole in the lid to allow the tubing to enter... and water sealed the tubing as well as the dowels holes.
Also added a 6" air stone placed in the center, a media bag of DI resin freefloating in the middle, and another bag of DI to the new filter. Here's a scan of some coins received today. These should be very good test subjects, with varying degrees of dirt (up to 8mm thick), patinas and encrustations.
During the interim, I tried a fish tank heater, but other than smelling like a sauna, I couldn't discern any difference.
My next step(s) will be to add a submersible water jet and to replace the wooden dowels with stainless all thread. The wooden dowels are beginning to sag from the weight and constant moisture.
After 2.5 days. These results aren't as good as what I was getting in the small 1 gallon tank, though they are still better than plain soaking. Something must have changed when I increased the volume. I may have to go back to small containers... and run 3 or 4 at once. But if you look at individual coins, you can see quite a difference still.