Hey, welcome to AA.
good to see everything is still doing well.
I've heard from different sources that the number of inches of fish is the real issue when stocking a tank, and from others that the number of fish is the issue. Which is it??
It's a combo of both in my opinion. On one hand, your system needs to have good filtration to allow your stocking to be maximized to the "inch rule" which is 1" per 5G of water. On the other hand, the aggressiveness and territorial nature of the fish you keep also limits your stocking.
With your tank, being that it's a Hex tank, it has the flaw of being short on surface gas exchange because of the tanks' geometry. Therefore, you shouldn't try to pack as many fish in there cause oxygen may be limited, and CO2
may be high.