those are what i call monster tanks.
i believe that most asians like me prefer to have a crowded tank. but i can say that the maintenance of such tanks are hell lots of work. i have to wash my filters every 2-3 wks and everytime the sludge is very thick. the peak of my tank was close to 40 fish in the range of 3"-18" in my 4'x2'x2'. now i "only" have 20+ fishes ranging from 3"-18" in the same tank.
when i had around 30 fish in there:
the above picture was taken during my water change. i have some driftwood and bogwood in the tank for the smaller fish to hide.
my current list of fish:
Polypteriformes:
3 x Endlicheri (Polypterus endlicheri endlicheri) (2 x 10" 1 x 18")
1 x Long Fin Senegal (Polypterus senegalus) (11")
1 x Albino Senegal (Polypterus senegalus) (10")
1 x Delhezi (Polypterus delhezi) (13")
1 x Ornate (Polypterus ornatipinnis) (5")
1 x Zaire Green (Polypterus retropinnis) (12")
Characin:
2 x Metynnis hypsauchen (5")
Catfish:
1 x Lima Shovelnose (Sorubim lima) (13")
1 x False Jaguar (Liosomadoras morrowi) (6")
2 x Spotted Raphael (Agamyxis pectinifrons) (3")
1 x L002 (Panaque sp.) (4")
1 x Albino Adonis (Acanthicus adonis) (6")
1 x Tigrinus (Brachyplatystoma tigrinum) (18")
1 x Gulper (Asterophysus batrachus) (5")
1 x L001 (Pterygoplichthys joselimaianus) (6")
Loach:
3 x Clown Loach (Chromobotia macracanthus) (3", 4", 5")
Stingray:
2 x Marbled Motoro (Potamotrygon motoro) (6", 12")
Spiny Eel:
2 x Fire Eel (Mastacembelus erythrotaenia) (18")
1 x Peacock Eel (Macrognathus siamensis) (4")