I have Oase biomaster 250 making grinding noise with very low water flow. I tried tilting, priming to make sure no air bubbles left and also waited for 24 hours .I have
Oase BioMaster Thermo 250 External Filter with Heater - AquaCave.com
BioMaster Thermo — OASE Living Water
Oase BioMaster Canister (external) Filters | Corydoras Zone Aquatics