How many fluid beds are you trying to run at one time? Everytime time you add a fluid bed to the same air pump. You will need to keep adjusting the air pressure to the previous bed. Because your lessing the air pressure to the bed that you already set. Probably takes me 10 or so minutes to adjust my beds. With a few tweaks after I start powdercoating. I also have to give each bed a good stir when I first turn on the air to the beds.

If drop a jig and it sinks to the bottom of the bed. That's s a good starting point of fluidity.

Here's a great video..

Liquid Sand Hot Tub- Fluidized air bed
Liquid Sand Hot Tub- Fluidized air bed - YouTube