Quite a number of interesting exhibits. Well done.
I realize this is in the fantasy section, but a few minor comments:
"Blue damselfish, peacock mantis shrimp"
- damsel doesn't stand a chance and would eventually end up as mantis shrimp food. Sure there are people that have tried it, but it rarely lasts. Mantis really belong in species-only tanks.
"greater blue ringed octopus"
- blue rings are indeed available in the aquarium trade (though they really shouldn't be kept by ordinary aquarists for obvious reasons!) and a well-connected public aquarium shouldn't have any problems getting them. Sure they're short-lived, but that's true for almost all octopus species, incl. all mentioned in this thread. It basically depends on getting breeding going, as done with various species at e.g. Monterey Bay Aquarium. However, their blue rings are barely or not at all visible most of the time. They just look like a tiny ordinary octopus. The blue rings are only really obvious when they're flared up e.g. when scared.
"Next is one of the larger tanks in this gallery, housing a bunch of fish that can't exactly be kept with live corals - so this tank is a large artificial reef tank."
- Most of the species you listed are entirely reef safe and wouldn't cause problems for live corals. The only exceptions are spotted knifejaw (eats sessile inverts and require subtropical water temperatures), angelfish (pretty much all angelfish species are risky, but it can be done, especially in very large tanks where a small amount of coral grazing isn't a big problem), butterflyfish (same as angelfish, although more problematic for the exclusive corallivores; none of the butterfly you mention are exclusive), sailfin snapper (eats sessile inverts).
"Volitan lionfish, antennata lionfish, leaf scorpionfish, stonefish"
- Stone will definitely eat leaf and antennata. May even try the volitan, although that combination has been done successfully at several aquariums.
"...chocolate chip starfish, feather duster..."
- Chocolate chip love to eat sessile inverts; they'll even have a go at small crustaceans if they can catch them.
"seadragon, golden neon goby"
- The goby is tropical (>72 F), seadragons are subtropical (<66 F, usually kept at 57-63 F). In any case it is currently impossible to source leafy, only weedy can be sourced.
"Blue spotted stingray, blue spotted ribbontail stingray, fiddler ray"
- same issue as above, fiddler is subtropical, others are tropical.
"Wolf eel, panamic green moray eel"
- same problem as above, although even larger difference in temperature requirements; wolf eel is a temperate species that only extends marginally into subtropical (and then typically in deeper sections where water remains cold). Would do fine in two tanks just above ("Barred sand bass..." and "California sheephead...").
"there are 9 different species of poison dart frogs living together, something rarely accomplished"
- With lots of space, it's easy enough to co-inhabit multiple dart frog species. The problem is that they can and often do hybridize. Among species you listed, the problems are: Green and black X bumblebee X dyeing; three-striped X pleasing; strawberry X harlequin. If you don't want hybrids, a good general rules is only 1 from each genus in a terrarium.
"dwarf green pike cichlid"
- Sure it's a dwarf, but they're aggressive and efficient hunters. They would love to be housed with rummynose, neon and similar sized fish! You'd have to accept that they're essentially feeders to the dwarf pike.
"redtail catfish... achara catfish, vulture catfish"
- once the redtail is fully grown, achara and vulture may well become food.
"fish hailing from the Mekong River"
- strictly speaking, a large percentage of those fish aren't found in the Mekong, but aquariums (and zoos) often use
very broad geographic definitions (e.g. Mekong = any freshwater fish from southern Asia).
"White cloud mountain minnow"
- require colder water than the rest in that tank, but would do perfectly fine in e.g. hillstream loach tank. Some of the Vietnamese Tanichthys are better able to handle warmer temperatures long-term.
"very slightly brackish... blue sheatfish... asian upside down catfish"
- neither of those can live in brackish water, even if only slightly. However, there are numerous other catfish species that do fine in brackish water.
"Asian yellow spotted climbing toad, emperor salamander"
- although I've seen places mixing these, it really isn't the best choice. During the summer their temperature preferences are roughly a match, but the rest of the year the emperor require colder temperatures.
"polleni cichild"
- goodbye to jewel (unless one of the large species) and kribensis cichlids, and Congo tetra. Risky for reedfish, too. Polleni's actually do well with other large Madagascar cichlids (Paretroplus, Ptychochromis) as long as there's plenty of space, but they also do fine with larger, robust African mainland fish.
"northern rosella, eastern rosella"
- doable, but would need a very large aviary with plenty of vegetation/other structures to limit line of sight. Rosellas can be rather unpleasant towards other rosellas and other parrots.
"Madagascar rainbowfish are common with private hobbyists, so they would be easy to find. I don't know if they're in public aquariums though"
- plenty in public aquariums too. However, while private keeper almost only keep Bedotia madagascarensis (often misidentified as B. geayi), a number of rarer relatives are kept in a few public aquariums, sometimes as part of endangered species breeding projects. I posted a longer comment about it here:
www.zoochat.com/community/media/madagascar-bedotia-amp-madgascar-pachypanchax-tanks.270972/
