Giant gourami question

[xraycer]

My brother used to have 17" rtgg in a 125 and it looked way too small for. He end up giving it away. It was one of the best looking rtgg i've ever seen

Yikes! At 17" that thing could barely turn around in a 125.

 

[MyGiants]

You could do it keep one. Nobody here going to advocate you do it. But they sell lots of giant redtails at small size in the market and not everyone's got a 300g tank. You could raise a 4-6" one for year or two before you could plan for a bigger tank.