Got a free 300 gallon....

[Cardeater]

Clown loaches big school.Siamese algae eater school. Clouded archers. Rare plecos.

 

[PYRU]

My votes for a big puffer Or some big knife fish with odd balls

 

[pancakes]

Ive seen a big 2k+ school of CLs in a 240 pretty cool

 

[krichardson]

Congrats on the tank....that's what you call a come up!

 

[neko1]

big puffer or some giant goby or group/pair of snakeheads

 

[piranhaman00]

Awesome dimensions! I feel like most 300s are in the 8x2 range. Love the 3' width!

You have many, many options. I like the rescue oscar idea.

 

[Ogertron3000]

South American mega tank, giant school of angels , massive school of columbian tetras , big group of geos and a big pack of cories cruising around the bottom. Heaps of wood and plants and maybe a few apistos in there too.
You'd see true natural behaviour that people don't normally get to witness.

 

[Gourami Swami]

I like the idea of getting rescue Oscars and other big cichlids from people with 30 gallon tanks. I see plenty of those on craigslist, etc. and feel bad for them. Your tank could be a cool little sanctuary.