I recently assembled an Intex above-ground pool with a DIY Biofilm Substrate Filter made out of two IBC totes.
Construction was based on the book How to Build a Natural Swimming Pool by Wolfram Kircher and Andreas Thon
The swimming pool is roughly 2.80 x 5.5 meters. I used two IBC totes instead of the recommended three (based on the area of the pool)
because I ran out of blocks on which to set the IBC totes. I also only filled them up halfway because the substrate I had access to was unwashed
and getting all of the dust out was extremely tedious (I ultimately gave up and let everything wash into the pool, used alum as a flocculant and vacuumed it out).
I bought a pump that's much more powerful than necessary because it was the only one in stock, and I wanted to get the project finished THIS summer.
I assume that the increased percolation rate will at least partially make up for the smaller (and frankly, shoddily constructed) filter.

We are roughly two weeks post-build and the water is quite clean. Haven't used any chemicals other than the alum. I vacuum it regularly with a small pool vac, and remove
dead bugs and leaves with a net. Here are some pictures:


Ground preparation for the pool




Supports for the IBC totes. There was a larger-than-expected height difference...




Water distribution pipework at the bottom of the IBC tote, before filling with substrate. In retrospect, one horizontal pipe would have been enough for even distribution...




A gravel and stone pathway to prevent the creation and propagation of mud into the pool




The water is crystal clear. Hopefully it stays this way...