You have 2.5 ft deep gravel for your water to upflow through as a filter? On the one hand the more media the longer it takes before a problem will show like clogging and channeling. The downside is how much shovelling of gravel and where to put it if there ever is a problem you need to go down there to fix and how do you not destroy the liner doing it? Don't get me wrong if I bought a house with your setup I'm sure I'd love it and use it but I would also have an exit strategy if something ever did go wrong. I'm just a worrier. Or too lazy to accept even a 20+ year maintenance cycle when it comes to shoveling gravelMine has been turned off during the hot of summer for a day or so. Turned off for 4 months over winter. I turn it back on, NEVER have a fish kill, never. The water ( in the spring) goes crystal clear within a few day from the winter murky look. I never get green water, minimal string algae. Do nothing but yank plants when they over grow.
I had a small bog on another pond it did just as good, Arizona.
In 2010 when I was researching the best way to build my pond here, I read a lot of posts from monster pond builders. The bog was highly talked about. I did not follow the "rules" 12-18 inches deep, etc, mine is about 2.5 feet deep. I also have high flow through mine, except for a small diversion to another pond all of the flow from my 6800 gph pump is sent through it.
I have never regretted having it, the fish and pond do great.
Not the best picture, this is the flow from the bog. My anti heron net is falling apart waiting for a new one to get here. It also weeps over the bog wall here and there. That rock is around 3 feet long.
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