Hi Sneezebeetle! Did you ever get this sorted out? Do you have any example pics you can share? One thing I've found on my Android phone that helps with better seeing the color in my corals pics is turning down the brightness before taking the shot. Assuming most Android phone camera apps work similar to each other, after you touch the screen to identify what you want it to focus on, a brightness dial bar also pops up on the screen. Try lowering the brightness a tad before taking a shot to see if that helps the wash out issue. Also, what filter combinations have you tried? And did you try using each of 3 color spectrum settings (15000 K, 20,000 K, or 23,000 K) your light has well? Just covering all of the bases.
As an example here's a shot I just took of my tank. I used an LG V35 phone with the IceCap Lens kit with the yellow 20,000 K filter attached. I adjusted the brightness down about halfway from the default setting before snapping the shot.
Hope to see pics of your nano tank in this month's Member Spotlight!