From reading and studying, NFT and DWC need a good filtration. Would a simple grow media bed with earth worms followed by a swirl filter be adequate?
Biofilter/GrowBed ----- Swirl Filter ----- NFT pipes ----- DWC bubble-style buckets
Does the swirl filter have to before or after the biofilter?
Depending on the size of your system and the size of the growbed, a media bed could function as a biofilter and handle all of your solid fishwaste.
I say after. I want all of my solids to get a chance to be digested by my worms. You do need to make sure to have enough media for the amount of fish. But I think most people prefer to not have to bother and don't want to worry about how efficiently their system is running. Putting the filter before the media you can overstock and overfeed your fish without clogging up your media beds. That's helpful when you are focused more on growing lots of fish to eat. If you care more about the plants then stock low and swirl after bio to clean for dwc and nft.
So, then there really isn't much need for the worms if the swirl filter is first?
I would say cut out the swirl filter, keep the worms. The swirl filter will collect large waste, while worms will get rid of it. Just from my point of view I think the worms would be more beneficial over the swirl filter.
If you have a bell siphon in the media bed, then chances are the large waste will not cycle back through the system before the worms get it. If it is a constant flow in and out, make sure the inlet and outlet are on opposite sides of the growbed. This way the large waste will have many chances to get caught in the media far before it gets close to the outlet.
For what its worth, I've had a problem with root matter and large fish waste in my vertical towers, so i'm installing a swirl filter with bypass inline to my towers and allowing the bypass to go to my horizontal beds. I'm basically using it to control what size waste goes where.
Yes, low stocking density producing less fish waste. Lot of advantages to having an AP system with this design. Less work and you don't have to deal with drastic swings in the water chem., minimizing inputs vs outputs, and more. In the true sense its a combination mechanical/bio-filter. I find though,that this type filter design works better when it has larger than normal capacity. If designed efficiently I think you can eliminate the added swirl/mechanical filter. I use my own design of a combination swirl/net filter, which performs great