I've got a 90 gallon aquarium that I inset into the living room wall (used a closet in the room on the other side of the wall for the tank to fit in) I have 3 different types of South American Anostomadae (Head-standers) in the tank. I have the about 4 of the Leporinus, 3 of the "Pencil Fish", and about 1/2 dozen of the regular anostomadae.
It used to be a saltwater reef aquarium, I had about 90 pounds of live rock, I had a head of sunflower coral, pulsating xinnia coral, kenya tree corals, mushroom polyps, etc. Had the metal halide lights, actinic light, UV sterilizer, chiller unit, protein skimmer, wet/dry filter, cooling fans, etc, etc, etc. It was a lot of work, and when I spent more time with it in the beginning, it was really something. I had everything on a schedule, did a 25% water change every month, used only reverse osmosis water to make up the new salt water with
I had everything so in balance, that I had a mated pair of skunk cleaner shrimp that would actually spawn, although, I think most everything they released got eaten.
(I called them 'fokkers' because the color scheme on them reminded me of a German fighter plane.)
Anyhow, at some point, water quality got out of whack, and I had issues with snot-grass (hair algae) as well as aptasia anenomes, and then I could never get the phosphate levels back to normal, despite water changes, etc. Then little by little, corals started dying off, the snot grass took over the live rock, and I threw my hands up with it, went to a freshwater tank.
I also have a 2000 gallon pond in the backyard with some large koi, a couple of them are over 2 feet in length. I use a regular sand filter for a pool to filter the water, as well as a UV sterilizer, along with a pre-filter box and an overflow weir. The water is filtered, then returned to the pond via a 4 foot high waterfall to provide aeration. All of this combined gives me crystal clear water that's clean enough to drink, despite it being well water from a shallow well with a lot of iron sediment. (I do have a water filter on the spigot that goes to my pond, to pre-filter the sediment out of the well water.)
In the winter time, I do have problems with herons, but we fix that by suspending a net over the pond, using strings from the limbs of the oak tree that hang over the top of the pond. The net goes on in November, when the bait fish leave the creek, and it stays until about March or April, when the bait fish return to the creek and the herons can go out there to hunt.