diff --git a/rllib/agents/dqn/apex.py b/rllib/agents/dqn/apex.py
index 7bc68be5b9ed..46743c1c91ed 100644
--- a/rllib/agents/dqn/apex.py
+++ b/rllib/agents/dqn/apex.py
@@ -40,7 +40,7 @@
 
 # yapf: disable
 # __sphinx_doc_begin__
-APEX_DEFAULT_CONFIG = merge_dicts(
+APEX_DEFAULT_CONFIG = DQNTrainer.merge_trainer_configs(
     DQN_CONFIG,  # see also the options in dqn.py, which are also supported
     {
         "optimizer": merge_dicts(
@@ -75,7 +75,10 @@
         # we report metrics from the workers with the lowest
         # 1/worker_amount_to_collect_metrics_from of epsilons
         "worker_amount_to_collect_metrics_from": 3,
+        "custom_resources_per_replay_buffer": {},
     },
+    _allow_unknown_configs=True,
+    _allow_unknown_subkeys=["custom_resources_per_replay_buffer"],
 )
 # __sphinx_doc_end__
 # yapf: enable
@@ -154,19 +157,36 @@ def apex_execution_plan(workers: WorkerSet,
     num_replay_buffer_shards = config["optimizer"]["num_replay_buffer_shards"]
     replay_actor_cls = ReplayActor if config[
         "prioritized_replay"] else VanillaReplayActor
-    replay_actors = create_colocated(
-        replay_actor_cls,
-        [
-            num_replay_buffer_shards,
-            config["learning_starts"],
-            config["buffer_size"],
-            config["train_batch_size"],
-            config["prioritized_replay_alpha"],
-            config["prioritized_replay_beta"],
-            config["prioritized_replay_eps"],
-            config["multiagent"]["replay_mode"],
-            config.get("replay_sequence_length", 1),
-        ], num_replay_buffer_shards)
+    custom_resources = config.get("custom_resources_per_replay_buffer")
+    if custom_resources:
+        replay_actors = [
+            replay_actor_cls.options(resources=custom_resources).remote(
+                num_replay_buffer_shards,
+                config["learning_starts"],
+                config["buffer_size"],
+                config["train_batch_size"],
+                config["prioritized_replay_alpha"],
+                config["prioritized_replay_beta"],
+                config["prioritized_replay_eps"],
+                config["multiagent"]["replay_mode"],
+                config.get("replay_sequence_length", 1),
+            )
+            for _ in range(num_replay_buffer_shards)
+        ]
+    else:
+        replay_actors = create_colocated(
+            replay_actor_cls,
+            [
+                num_replay_buffer_shards,
+                config["learning_starts"],
+                config["buffer_size"],
+                config["train_batch_size"],
+                config["prioritized_replay_alpha"],
+                config["prioritized_replay_beta"],
+                config["prioritized_replay_eps"],
+                config["multiagent"]["replay_mode"],
+                config.get("replay_sequence_length", 1),
+            ], num_replay_buffer_shards)
 
     # Start the learner thread.
     learner_thread = LearnerThread(workers.local_worker())
@@ -285,4 +305,5 @@ def apex_validate_config(config):
     validate_config=apex_validate_config,
     execution_plan=apex_execution_plan,
     mixins=[OverrideDefaultResourceRequest],
+    allow_unknown_subkeys=["custom_resources_per_replay_buffer"]
 )
diff --git a/rllib/agents/sac/apex.py b/rllib/agents/sac/apex.py
index cb2d43103040..fade18628226 100644
--- a/rllib/agents/sac/apex.py
+++ b/rllib/agents/sac/apex.py
@@ -36,7 +36,10 @@
         # This only applies if async mode is used (above config setting).
         # Controls the max number of async requests in flight per actor
         "parallel_rollouts_num_async": 2,
+        "custom_resources_per_replay_buffer": {},
     },
+    _allow_unknown_configs=True,
+    _allow_unknown_subkeys=["custom_resources_per_replay_buffer"],
 )
 
 
@@ -48,4 +51,5 @@
     name="APEX_SAC",
     default_config=APEX_SAC_DEFAULT_CONFIG,
     execution_plan=apex_execution_plan,
+    allow_unknown_subkeys=["custom_resources_per_replay_buffer"]
 )
diff --git a/rllib/agents/trainer.py b/rllib/agents/trainer.py
index 1ec3a5ad7978..d6ff21261146 100644
--- a/rllib/agents/trainer.py
+++ b/rllib/agents/trainer.py
@@ -1174,7 +1174,8 @@ def resource_help(cls, config: TrainerConfigDict) -> str:
     def merge_trainer_configs(cls,
                               config1: TrainerConfigDict,
                               config2: PartialTrainerConfigDict,
-                              _allow_unknown_configs: Optional[bool] = None
+                              _allow_unknown_configs: Optional[bool] = None,
+                              _allow_unknown_subkeys: Optional[List[str]] = None,
                               ) -> TrainerConfigDict:
         config1 = copy.deepcopy(config1)
         if "callbacks" in config2 and type(config2["callbacks"]) is dict:
@@ -1188,8 +1189,10 @@ def make_callbacks():
             config2["callbacks"] = make_callbacks
         if _allow_unknown_configs is None:
             _allow_unknown_configs = cls._allow_unknown_configs
+        if _allow_unknown_subkeys is None:
+            _allow_unknown_subkeys = []
         return deep_update(config1, config2, _allow_unknown_configs,
-                           cls._allow_unknown_subkeys,
+                           cls._allow_unknown_subkeys + _allow_unknown_subkeys,
                            cls._override_all_subkeys_if_type_changes)
 
     @staticmethod
diff --git a/rllib/agents/trainer_template.py b/rllib/agents/trainer_template.py
index 1192d4751e2c..b194330fa18f 100644
--- a/rllib/agents/trainer_template.py
+++ b/rllib/agents/trainer_template.py
@@ -64,7 +64,8 @@ def build_trainer(
         mixins: Optional[List[type]] = None,
         execution_plan: Optional[Callable[[
             WorkerSet, TrainerConfigDict
-        ], Iterable[ResultDict]]] = default_execution_plan) -> Type[Trainer]:
+        ], Iterable[ResultDict]]] = default_execution_plan,
+        allow_unknown_subkeys: Optional[List[str]] =  None) -> Type[Trainer]:
     """Helper function for defining a custom trainer.
 
     Functions will be run in this order to initialize the trainer:
@@ -112,6 +113,8 @@ def build_trainer(
 
     original_kwargs = locals().copy()
     base = add_mixins(Trainer, mixins)
+    if allow_unknown_subkeys:
+        Trainer._allow_unknown_subkeys += allow_unknown_subkeys
 
     class trainer_cls(base):
         _name = name