Wow... good to know bout that poison.. altho I should prolly be dead at this point since I've touched mine regularly for quite some time... enough alchohol will kill anything I suppose!
Anyhow, yup, like they all say, that tank is headed for a crash.
I've heard of some mandarins eating frozen mysids, but it's fairl rare.
The angel will go crazy or be deformed or just plain die due to the space alotted to it.
The jawfish won't be terribly happy either, it needs a deeper sand bed (hopefully you have the right type of sand, elsewise it'll be miserable).
I can also see the emeralds feasting on anything moving very slowly at night as the crabs get bigger (tends to happen when they grow, they needs lots of foods...or rather want lots of foods... and claws are dangerous).
Please do take the advice.. I lose things to infections etc.. that's part of the game and can be minimized with QT and good husbandry..
You'll lose things just because the ocean is way to small for em...and nothing short of taking some specimens back (the aforementioned ones would be best) and a little magic is really going to change that in the long run.