You ask 'is 7" to shallow for shrimp and fish' but you don't specify which species. That depth is ideal for most Labyrinth/Anabantoid species, e.g. gourami, betta, etc. It's conducive to breeding.
On another note, is this project for aesthetic purposes? If not, it's a waste of money. $100 (as noted in the provided link) for a surface area of 23.6" x 11.8" vs for example $40 for a tank with a surface area of 48.3" x 12.8" (40 gallon tank)
Then just simply fill the 40 gallon with only 7" of water. This would also give the option of increasing the depth at some point in the future, should you ever change your mind or simply want to try another project. <$100 could even buy two 40g tanks each with a surface area of 48.3" x 12.8"
Surface area trumps volume. >Twice the bioload of shrimp and fish for <$ than the 8g
I notice a troubling trend in modern aquarium keepers, where the measure of welfare seems to be steeped solely in terms of survival: if the fishes live, things are good, if the fishes die, things are bad. It is an inappropriate position to take. [Nathan Hill in PFK]