Would 3 platies be okay in the aqueon column tank? there are live Java ferns and anubias in the tank as well. they'd be with three endlers.
The dimensions of a 15g column are not long enough for platies. I personally don't like to keep them in tanks under 20 gallons. Their max size is about 2.5-3 inches once they reach full maturity.
I would do a few more endlers. They are pretty social.