Well I finally got around to doing this - I used a spare mini internal filter that I use in my other minibows instead of the filter that came with it. Figure I'd stick with what I know will work well. I used a bit of media from another betta tank and moved all the gravel and about half the water over. Since it's just one little female betta the gravel wasn't too dirty.
Anyhow, the minibow doesn't look as good in this space as the other tank did (the other was round with an ivory lid and this minibow has a black hood and is the standard minibow shape - the tank is viewed from the side so the round shape worked well) but my betta girl kept getting into the UGF tube and going down under the plate. I saw no easy fix to stop her from doing this and was afraid she'd get stuck down there one day and die if she couldn't get to the surface for air. Plus the tank was pretty small and I really hate going under 2.5g for a betta - even a tiny girl.
So she's swimming around checking things out and altho I don't like the look as much it's better for her and we all know it's all about the fish, right? I wish they made an ivory or more neutral colored minibow though.
Thanks for all your help guys.