honestly, if you have a "back up" tank, take a big front glass and go for seeing your rays and others to the bottom of the tank... but if you don't have a back up tank, you'll probably need a "safe box" in concrete (as I have) to stock your monsters if once, you'd have to make a modification on your main big tank. It's not that easy to stock monsters of more than 1 meter wide (Arowanas now and female leopoldi stingrays in a few years). That was my choice and compromise... safety first...
considering Panaque and Stingrays, they do use the hardscape of the tank to climb on it... and every evening when feeding or going around this tank, I see the rays on the background 2/3 part of the tank's bottom... with my concrete wall, I "loose" 1/3 of the front bottom vision when facing the tank. But it's not that important...
the concrete wall was poured into a wooden frame, with steel bars inside it to consolidate it all. I must find some picture of it under construction... let me a while to repost them...
the filtration is the small OASE SmartPond 140000 for a part, but most of it is a pool sand filter (90 liters sand, for 12'000 l/hour, 3x7 hours a day) for biological/mechanical filtration
the plants simply receive a drop-by-drop tap water from above, by a thin pipe which delivers 4'000 liters a week, and I have a overflow driving directly into the house waste waters evacuation system.
considering your last request, I unfortunately never have been able to shoot a decent video of an insect hunting game... with big green grasshoppers, it's very impressive... but it's way to difficult to shoot because of the plexiglass suspended doors... and I can't leave them open without the risk of finding an arowana dead and dry on the ground...