In fact I had intended to start a new WTT thread to show my (if even brief) experience with it -- and to solicit opinions & first hand experience exactly like RD nicely gave, but for now will continue this thread's set-up theme.
First I got rid of the hospital like look of the white acrylic strips bordering top and bottom tank, simply by covering them with black masking tape; imo it looks heaps better.
And here's what I've put in for filtration initially:
1) 1 pre-seeded big sponge filter -- frankly with the current bio-load the tank has, I'd bet money this 1 simple sponge filter could support enough beneficial bacteria to take care of 1 juvenile Arowana in that 7 ft tank no problem for some time to come, especially if I'm as usual zapping out waste every day with my handy battery powered tank siphon.
2) To the left of that is a Sonic power head (2000 l/hr) that is feeding a Sunsun HW-603 pre-filter and a Sunsun 704a canister (no UV as I plan to add a separate unit later) in a tub behind the tank. The 704 is filled entirely with pre-seeded, good quality Ocean Free Pro 3D bio-media.
I know it's generally not a good idea to have a power head connected to a canister filter -- but I tried all night to get the pre-filter/canister combo primed without one, but just couldn't -- and even if could final return flow rate would have been abysmal. Once I put on the Sonic it's been working perfectly, smooth flow, no air bubbles, no crazy sounds and no overheating of the 704's pump even though the room is a pretty constant 80F+.
Both the Sonic and the 704a have (published) flow rates of 2,000 l/hr, so maybe they're a good match, time will tell. I also know the 603 is not rated for this flow, but have been using 2 of them on other tanks for about 2 years (also above stated flow rate) and haven't had a single problem so far, knock on wood. In all these set-ups though as a bit of peace of mind, in case any leaks develop I have very loud Doberman Security water alarm in the tubs.
3) On the right side of the tank is a 2,500 l/hr Sonic pump that is feeding a 15-tray shower/trickle filter I ordered online from China. In fact I was planning to install one of these even before I saw his video (I'd seen them on some vids of Singaporean & Chinese tanks), but PondGuru has a good video on YouTube about these filters, he seems pretty keen on them. They're not everyone's cup of tea as they can't be easily hidden, but I personally don't mind this and can see they make a great environment for beneficial bacteria.
As a side note though, I tried 4 smaller feeder pumps, starting at 800 l/hr then working up, and none of them could pressure the water enough to go out decently in the last 2 trays until I put in the 2,500 l/hr unit. I also expanded the holes of the last shower ring a bit, which helped.
4) Under the return of the shower filter I have a Sobo mini-powerhead to help distribute good water falling from above, while also helping to push any waste toward one end of the tank for easier cleaning.
5) Finally, for aeration I got another Hailea CP-60 AC/DC air pump, which will automatically change to its internal battery when the power goes out. This pump has an output that way exceeds my needs on this tank, but the next size down ac/dc pump I could find is too small.
So with current bio-load I would maintain this set up is more than enough filtration, though I do plan to add a good-sized UV sterilizer later this month. In fact a lot of the bio-media is probably just sitting there largely unoccupied because not enough food source to support the additional BB, but it's there if needed and if I later add a tank mate or two.
And it's all pretty simple -- all I need to do (besides my usual daily zap of waste with vacuum), is clean out the pre-filter on the canister maybe twice a month and clean/change the top level mechanical filter pads on the shower filter as required now and then.
Happy to have any opinions or questions.