In this video, the designer deviated from the age old undergravel filter (UGF) with:
1. bottom drain to extract waste under the UGF; I have that in my pond and it worked well. Most ponds have one of them
2. the filter was more elevated from the tradition UGF, almost 1 inch (2 cm?), Does the distant matters in how UGF works?
3. a felt like sheet between the filter and gravel.
thoughts?

1. bottom drain to extract waste under the UGF; I have that in my pond and it worked well. Most ponds have one of them
2. the filter was more elevated from the tradition UGF, almost 1 inch (2 cm?), Does the distant matters in how UGF works?
3. a felt like sheet between the filter and gravel.
thoughts?
