I would say the biggest filtration unit you can find, and buy two of them. You list three of the "dirtiest" species of big fish, with the Oscars being number one filth maker.
I disagree that the Oscars are likely to harass the Arowana specifically, but I wonder about the shape/dimensions of the tank, as the Arowana requires a considerable distance for swimming room. With all those Silver Dollars, the Oscars will be too busy to worry about a surface dwelling fish. And 4 Oscars in 500 gallons aren't going to get too nasty with one another, either.
I would not use Clown Loaches as bottom fish. Oscars aren't familiar with the warning that the bright orange and black stripes are meant to send. Clown Loaches have switchblade spines under their eyes, used mostly for defense. You could easily lose an Oscar, or at least have it damaged badly. It's even possible that an Oscar might get so far as to get a Clown Loach in its mouth, at which point both fish will die.
Plecos are iffy. Sometimes the Oscars ignore them, sometimes they do not.
I wanted to make diysump filter so thats why i asked for volume of media and liters per hour.second thing is that aguarium is 2.4 meters long 1 meter wide and 60 cm deep(i make bigger if i need but i think this is good measurment. With driftwood for hiding plecos or somethibg like it
And becausse i grow chickens quails rabbits and fish in my pond(carp ,red fin perch and wels catfish) and farm of earthworms and maggots. Can i use them for fish feeding (not live rabbits and other things but a piece of boneless fillets and their organs a s for example hearth
I would think a 75g (284 liter) would be idea for your sump. With that said, the liters per gallon will depend on the pump you will buy. There are plenty of pumps that are designed to push our 400+gallons or even more. Obviously the more GPH the better.
I would check sites like Amazon to see if they have high GPH pumps.
Here is my advice, for what it's worth. If you're going with a sump the general rule that I've heard is 1/4 of the display volume for the sump so for a 500 gallon display tank you would want a 125 gallon sump. For flow, well there flow through the sump and circulation in the tank. For flow through the sump I'd say try for 10x the system volume (display+sump) per hour so around 23660 lph. For that you would probably be looking for submersible pond pumps to keep the price reasonable. The pumps I'm familiar with in the saltwater side that can do that are things like the Abyzz A400 DC pump that is about $2500.00USD where you could look at something like an Alpine PAL6550 pond pump (6550GPH) for around $200.00 USD although pond pumps are generally louder. For safety I would recommend having a spare pump in it would take more that a day or two to get a replacement. For circulation I would get powerheads/wave makers that can give you the turnover, in my (smaller) saltwater tank I have about 70x turnover. For a 500 gallon tank you would be looking at several powerheads/wave makers place throughout the tank. I would also recommend an aquarium controller or some sort to manage the tank.