Sorry you haven't had a answer yet.
The tank is a bit small for a clam as the water parameters are hard to keep perfect in this size tank.
Regarding the aquabeam yes you could add this to the tank (you could even remove the power compacts from the lid and put the aquabeam in their place. However I don't honestly know if this would be enough for a clam or not.
For anyone else with more knowledge of the aquabeam or clams the orca 450 is about 18inches deep and around 58L