Aye of course. The pipe drains into the return chamber, there's no filter sock. In that chamber there are some off cuts of course filter foam just floating about and some bits of alfagrog. In the next chamber is more filter foam at course then medium then fine densities. This is sold as for pond filters. Cost about £15. There's the duckweed and salvinia natans floating. Then into the big chamber. In here is more alfagrog (2kg in total), some elodea and some cabomba and also some bog standard spider plants growing in clay pebbles in a shower caddy. The water falls over a weir into the final chamber, as it does it runs through more spare filter foam that I just attached with clothes pegs, so its like a trickle filter. Final chamber has two more shower caddies sitting on the bottom with peace lillies and echinodorus barthii in them, all the leaves are emersed, planted in clay pebbles again. Then return pump back up. And there's also a wee bag of activated carbon. The sump is lit for 12 hours with a cheap interpet led on the reverse to the main tank. So far so good.
If I was doing again I'd ditch the cabomba, its shedding a lot of foliage. I'd also maybe get a big floater like pistia instead for the main chamber and avoid any submersed growth at all.
I've not used the ATU chamber yet.
All in all it seems highly effective at the moment