Modern algorithmic market making faces an inherent trade-off between risk management and various forms of market impact. Dealers in the FX market increasingly offer access to internal liquidity pools, which, in addition to providing clients with an alternative means of execution, can create further opportunities for risk management. Modelling and investigating these opportunities naturally leads to the question of so-called passive market impact. We subsequently derive a model of passive market impact from microscopic principles that can be solved in closed form. These models are calibrated with FX and equities market data.