And I do have plants in my tank, do I need to get a higher wattage bulb?
And how about CPD’s? They are small!
And even people on TFF have HR, and bettas in the same tank. @Fishmanic, I know that you have them, how is that working out?
We (several of us) already said your light is fine.
CPD's will work in this tank but only a group of CPD, not with a Betta or anything else (in fish). That was previously said too.
As for Harlequin Rasbora and Betta, this is a risk and it is simply not fair to the fish to risk it. Bettas are not community fish, everyone from Neale Monks down will tell you this. Assume a species will behave normally and not be an abnormal exception. You already said you only have the one tank for the danio, so what will you do if your Betta and Harlequins start having issues? Understand the needs and behaviours of a species and if you want to keep that species then provide accordingly. That is the only fair (to the fish) approach in this hobby.
I mentioned somewhere that an individual went over Niagara Falls the other day and survived; you cannot take that one exception as "proof" anyone can go over and not end up dead.