I would really like to build a pool for the kids to swim in, and I want it to be chlorine-free. I have How to Build a Natural Swimming Pool by Wolfram Kircher and Andreas Thon, so I'm familiar with some of the theory.
Unfortunately, for a wide variety of reasons (permits, not knowing what I'm doing, seven species of venomous snakes that I don't want near my pool, etc) it appears that I am constrained to installing an above-ground pool (Intex, Bestway, etc).
I would like to apply natural swimming pool principles to this project, but I can't seem to find anything on Google (or Permies) where this was done with a prefab above-ground pool. I hope I'm not the first person to come up with this,
and that there are people here who can provide some tips.
1. I would like to use a BSF (Biofilm Accumulating Substrate) filter, which is basically a container filled with substrate (gravel, zeolites, etc) on which beneficial bacteria can form a biofilm. The water needs to flow rapidly and evenly through the container. Benefits:
Efficient at destroying harmful bacteria
Efficiently removes phosphorus from the water, which limits the ability of algae to thrive
Reduces or eliminates the need for plants, which is useful given my constraints
Not having plants allows me to keep the pool covered when not in use, greatly reducing water loss to evaporation (useful with the hot dry summers we have)
I haven't found any practical advice on how to build one outside of the book, and the book didn't go into a lot of detail.
2. I was thinking of putting in a UV filter somewhere along the flow. I know this contradicts the "Natural Pool philosophy" (the book explicitly states this) but I am not the purist I was when I was twenty.
It's important that the water be sanitary. A UV filter does not affect the microbial environment in the BSF nor does it hurt my kids. Any thoughts? I can be convinced that they are unnecessary...
3. Google, YouTube, Pinterest, etc are filled with multiple examples of home-made pond filters using a five-gallon bucket filled with gravel/bioballs/old sponges etc. Amazon also has multiple "biofilters" for sale - I can only assume that they work using similar
principles to the BSF - a substrate for beneficial bacteria to grow on and do their magic, with the occasional back-washing to prevent an old and dying biofilm from releasing nutrients into the water. These filters appear to be intended for fish ponds and not human use,
but from what I can gather from the videos, the water appears to be quite clear, so the filters are presumably managing to remove the nutrients that the fish deposit. I also see videos where people swim in their koi ponds - can a simple five-gallon bucket filter manage
to keep a pool clean enough for human use? The recommendations in the book are that a BSF should be 10-25% of the total area (10% only if installed by a professional), so am I missing something here? Some of the filters on Amazon appear to use some sort of sponge-like media,
and a lot of the homemade filters use old dish sponges - are these media so much more efficient than gravel that they can manage the nutrient load with such a small filter? I would love to just build a few filters using five-gallon buckets.
Even if the filter needed back-washing on a weekly basis, it would be much simpler and cheaper to switch out buckets than to build a much larger BSF.
If anyone has any experience with a project like this I would greatly appreciate any advice I can get.