Quick question, would a Finnex LED 12" be "high" light for a 7.5 gallon 12x12x12 Mr aqua cube? Is that good enough to grow HC, DHG, Riccia and needle leaf ludwigia?
If I read the charts correctly I think that you will be around 50mmol in a 12" cube tank if you use the Ray 2. Maybe down to 40 or so depending upon the details of the 12" version of the fixture.
That borders on high light. Depending upon who you ask it should grow just about everything. Might be pushing the edge of where you need to run CO2 though.