Many who are not yet YardCrap members are allowed to read this section, so maybe you are here after a google search of these.

I have played with that (home made filters) for over 20 years.
Do they work, yes, they do if you know what a filter is for.

Pros:
-- fun to make
-- maybe cheaper ?

Cons
--- folks not understanding the purpose of a filter
--- cleaning them

All filters must be cleaned. Any who say different --> lie.
Using something like a 55 gallon barrel is good, but cleaning is very hard. No matter what media you use, cleaning it will be very, very hard, so plan how to do that when you make your "skippy".

The purpose of a filter is to keep critters healthy by amplifying the nitrogen cycle using a small area.
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It is not to keep the water clear, but if set up right will aid that. As it aids that, it gets full of crap. That crap must be cleaned out.
Cleaning up a large tub of sponges or bio balls is tuff, not worth the effort. Starting fresh puts critter lives at risk until it is again "established" (full of bacteria). Not cleaning it is a time bomb of death.

Garden ponds and aquariums are the same.

If you seek a pleasant garden pond (or aquarium) with critters -- read some as to it all on my threads at YardCrap or that of any one with a clue.