You don’t want to restrict the pump flow. Instead add a t with a ball valve and pump the excess water back to the tank for additional aeration.
The 94 gallon bed will not drain the tank all that much once you fill it with the hydroton. Hydroton will take up 60% of the volume of the bed.
Lots of aeration is good. You can almost never have too much. I use the rechargeable backup type for extra piece of mind in case of power outage.
I think the silver perch are only available in Australia unless you get some at a pet store, but that may cost you.