LOL Waterbug is being facetious because of his contempt for those “all in one” filters. I tend to agree somewhat, especially in respect to their biological part of them. Take my own pressure filter, it actually works ok as a mechanical filter, although it’s a pain in the @$$ to clean, and it has a built in UV light, which works well, but the biological part of it is a joke. It has a few bio-balls that float around in the bottom portion of the thing where the bacteria colony is suppose to grow and do it’s stuff, and make no mistake, in that respect it does work, but on the grand scheme of things the amount of bacteria that grows in there is a small drop in the bucket compared to what is going on everywhere else in the pond.
Waterbug has also expressed a distain for Skippy type filters also, for the same reasons, but I believe they have value for home ponders because they are cheap to build and easy to experiment with. I have never built or used one, but I can see how they could be made into decent mechanical filters if you used the right type of media. Also because they open on the top and readily accessible you can see what’s going on in there, unlike a pressure filter.
As for biological filtering, I agree with what Waterbug has said many times, a water garden may never need any type of separate biological filter, it really depends on your fish load. The whole pond functions as a biological filter, the sides of the pond, the plants, and even the fish themselves have beneficial bacteria growing on them. Adding a few bio-balls or a bucket of lava rocks doesn’t amount to a hill of beans when you compare it to all the other surface area in your pond.