I think the problem may be that you're a follower of the ancient and now-disproven "Inch per gallon" theory. Carnivores and fish with deep bodies (ie, wide fish) need closer to 2 gallons per inch, minimum. Plecos as well. After research though, to what I can see IF you have a true gold nugget "L-18", then about 8 inches is the max. When it gets to about 6 inches, you should start looking for a new tank (or rehouse him).
If you can get a bigger tank, do so.
Bettas are a prime example of fishkeeping- They live for about 2-3 years in the wild before being eaten, killed etc. So people assume that's their max life span, and brag when their betta lives 3 years in a jar.
(I forgot the university..) did a study where they kept a Betta in a 20 gallon, pristine water, quality live foods, and even chased it around with a net to give it cardio exercise everyday. Guess how long it lived? Just about 11 years. (There's another study being run now, and he's going strong at 9 years. We'll see.)
Everyone else though-
making fun of the OP or repeating the same things that have been said isn't going to help anyone. Encourage, and maybe OP'lll come around. eventually.
The last thing we wanna do is drive off the OP (I've seen it happen many, many times.)