I had a smaller 12-18” deep pea gravel bog initially, and while it did the job somewhat ( it was undersized for my pond) my pond although large (10,000gallons)has alooot of fish (koi, orfes catfish )in it as well as turtles. So, I decided to upgrade the bog with the aquascape method and had the room to make the bog much larger. Nothing wrong with the pea gravel and pipe method, it works too. Mine worked for 10 years and still would, but I like to tinker with stuff.
To me the biggest difference between the two methods is the aquascape method lets me clean the silty gunk out of the bottom of the bog via a pump dropped down in the snorkel and prevents channeling of the incoming water as it flows up. Just a more efficient way to remove what can contribute to degrading water quality, as opposed to the pea gravel method. Mind you after 10 years my pea gravel bog never clogged or anything but the plants would divert water over the edges.....my fault for not making the sides of the bog tall enough.
I would not do the aquascape wetland filter method without aqua blocks though, as the idea is as the water comes in it slows down and the fine sediment settles out and works its way to the lowest point, Having a bunch of large rock in there on the bottom might prevent the sediment from working its way to that lowest point.
As for depth of a pea gravel bog
@addy1 has a bog that is at least a few feet deep and roughly 10 years old or more and has had no issues with it being that deep. So if you want to go that way I wouldn’t bother filling the hole back in some, I would just lay the pipe and bury it in gravel.
