Frag tank depth?

Completely new to this propagation stuff so I need a little help here. I want to squeeze a small DIY glass tank under my display and above my sump, yes it sounds cramped under a 72 bow . So I can fit a 19"x9.5"x 8" deep tank but that leaves little room for hanging a light and hand space in general ... Will a 6" deep tank be too shallow ? Lighting will be maybe a small T5 or dimable LEDs DIY . I want to keep my sump area neat and easy to access so a 6" tank will help .. Input please ?

 

It all depends on how big the frags are that you want to keep. 6" of water would be fine for most, if they are on the bottom of the tank.

You will also want to consider the fact that at that depth any light you have above the tank will need to be smaller than you'd normally need as 6" won't affect the PAR very much and you may bleach them if it's too strong.