Many fish do this for many different reasons commonly. However. The best way to cope is to just keep offering food (take out uneaten food after awhile). If a fish is hungry, they will eventually eat anything. It could just be from stress or something of the sort.
My local fish store ALWAYS has many gourami types in stock. Their pearl tank has at least 25 of them currently. No, they are not rare in all places. I agree, ask to speak to a manager at whatever shop it is that you go to. They will more than likely order you something if you want it and they...
I would recommend a spiny eel. A fire eel would do great. They are perfect for a tank of that size, just provide sufficient hiding spots. They like caves and like to burrow in sand. They will also dig under things so make sure all of your ornaments or w/e you have in the tank are on the glass...
I used to keep my 15 neons in my 55 along with 8 pristella tetras and 8 serpae tetras, and some plecos as well. My tank was very heavily planted but I thought it gave it a very natural look. and if you want to fill in that extra room in your tank, throw in some live plants. Not only do they look...
Any pump is quiet as long as you keep a cloth or something under it. And yeah, It's a pain having to hear pumps and stuff in the middle of the night. I have a 55 gallon cichlid tank and a 29 gallon marine tank in my bedroom. Gets kinda noisy sometimes (all the time).
Is it an adjustable heater? If so, make sure you did not accidentally turn it up higher than it needs to be. Try lowering it. (sorry, I know you're not stupid). But I use junk w/e heaters like aga. I don't recommend them for being superior to any others but they get the job done.