diff --git a/stac_fastapi/pgstac/app.py b/stac_fastapi/pgstac/app.py
index e4e07141..7d22df8f 100644
--- a/stac_fastapi/pgstac/app.py
+++ b/stac_fastapi/pgstac/app.py
@@ -83,15 +83,12 @@
 post_request_model = create_post_request_model(extensions, base_model=PgstacSearch)
 get_request_model = create_get_request_model(extensions)
 
-# will only use parameters defined in collections_get_request_model
-collection_search_model = create_post_request_model(extensions, base_model=PgstacSearch)
-
 api = StacApi(
     settings=settings,
     extensions=extensions + [collection_search_extension],
     client=CoreCrudClient(
         post_request_model=post_request_model,  # type: ignore
-        collection_request_model=collection_search_model,  # type: ignore
+        collections_get_request_model=collections_get_request_model,  # type: ignore
     ),
     response_class=ORJSONResponse,
     items_get_request_model=items_get_request_model,
diff --git a/stac_fastapi/pgstac/core.py b/stac_fastapi/pgstac/core.py
index d8afa18c..a7c322e9 100644
--- a/stac_fastapi/pgstac/core.py
+++ b/stac_fastapi/pgstac/core.py
@@ -1,5 +1,6 @@
 """Item crud client."""
 
+import json
 import re
 from typing import Any, Dict, List, Optional, Set, Union
 from urllib.parse import unquote_plus, urljoin
@@ -13,7 +14,7 @@
 from pygeofilter.backends.cql2_json import to_cql2
 from pygeofilter.parsers.cql2_text import parse as parse_cql2_text
 from pypgstac.hydration import hydrate
-from stac_fastapi.api.models import JSONResponse
+from stac_fastapi.api.models import APIRequest, EmptyRequest, JSONResponse
 from stac_fastapi.types.core import AsyncBaseCoreClient, Relations
 from stac_fastapi.types.errors import InvalidQueryParameter, NotFoundError
 from stac_fastapi.types.requests import get_base_url
@@ -38,7 +39,7 @@
 class CoreCrudClient(AsyncBaseCoreClient):
     """Client for core endpoints defined by stac."""
 
-    collection_request_model = attr.ib(default=PgstacSearch)
+    collections_get_request_model: APIRequest = attr.ib(default=EmptyRequest)
 
     async def all_collections(  # noqa: C901
         self,
@@ -83,7 +84,8 @@ async def all_collections(  # noqa: C901
 
         # Do the request
         try:
-            search_request = self.collection_request_model(**clean)
+            search_request = self.collections_get_request_model(**clean)
+            print(search_request)
         except ValidationError as e:
             raise HTTPException(
                 status_code=400, detail=f"Invalid parameters provided {e}"
@@ -93,7 +95,7 @@ async def all_collections(  # noqa: C901
 
     async def _collection_search_base(  # noqa: C901
         self,
-        search_request: PgstacSearch,
+        search_request: APIRequest,
         request: Request,
     ) -> Collections:
         """Cross catalog search (GET).
@@ -107,8 +109,12 @@ async def _collection_search_base(  # noqa: C901
             All collections which match the search criteria.
         """
         base_url = get_base_url(request)
-        search_request_json = search_request.model_dump_json(
-            exclude_none=True, by_alias=True
+        search_request_json = json.dumps(
+            {
+                key: value
+                for key, value in search_request.__dict__.items()
+                if value is not None
+            }
         )
 
         try:
@@ -533,7 +539,7 @@ def clean_search_args(  # noqa: C901
             filter_lang = "cql2-json"
 
         base_args["filter"] = orjson.loads(filter_query)
-        base_args["filter-lang"] = filter_lang
+        base_args["filter_lang"] = filter_lang
 
     if datetime:
         base_args["datetime"] = format_datetime_range(datetime)
diff --git a/tests/api/test_api.py b/tests/api/test_api.py
index 83589d08..33335c13 100644
--- a/tests/api/test_api.py
+++ b/tests/api/test_api.py
@@ -730,23 +730,21 @@ async def get_collection(
     ]
     post_request_model = create_post_request_model(extensions, base_model=PgstacSearch)
     get_request_model = create_get_request_model(extensions)
-    collection_search_model = create_post_request_model(
-        extensions, base_model=PgstacSearch
-    )
+
     collection_search_extension = CollectionSearchExtension.from_extensions(
         extensions=extensions
     )
-    collections_get_request_model = collection_search_extension.GET
+
     api = StacApi(
         client=Client(
             post_request_model=post_request_model,
-            collection_request_model=collection_search_model,
+            collections_get_request_model=collection_search_extension.GET,
         ),
         settings=settings,
         extensions=extensions,
         search_post_request_model=post_request_model,
         search_get_request_model=get_request_model,
-        collections_get_request_model=collections_get_request_model,
+        collections_get_request_model=collection_search_extension.GET,
     )
     app = api.app
     await connect_to_db(app)
diff --git a/tests/conftest.py b/tests/conftest.py
index e1dea234..17bfdf63 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -151,16 +151,13 @@ def api_client(request, database):
     )
 
     collections_get_request_model = collection_search_extension.GET
-    collection_search_model = create_post_request_model(
-        extensions, base_model=PgstacSearch
-    )
 
     api = StacApi(
         settings=api_settings,
         extensions=extensions + [collection_search_extension],
         client=CoreCrudClient(
             post_request_model=search_post_request_model,
-            collection_request_model=collection_search_model,
+            collections_get_request_model=collections_get_request_model,
         ),
         items_get_request_model=items_get_request_model,
         search_get_request_model=search_get_request_model,