i like the bubble trap at the end. the way i make mine, i only put 2 partitions for the bubble trap- the first is solid from the bottom up, and the second has the gap at the bottom. the idea is, the bubbles go over the first partition and head down to go under the second partition, about half way, where they do an about face and rise back up, not making it to the return area.
i always found if i had the water come over a last partition, bubbles would form as the water came crashing down there. especially when the water level was a bit low.
nice and simple, like this 40 breeder-
or this 55 gallon-
besides maybe a filter sock, i agree completely about the eggcrate filter pad levels. any carbon or GFO
could be implemented via HOB
reactors, and i would not want to deal with multiple filter pads like that. .