diff --git a/.github/workflows/run_all_tests.yml b/.github/workflows/run_all_tests.yml
index 308c56347..d5f8afc7f 100644
--- a/.github/workflows/run_all_tests.yml
+++ b/.github/workflows/run_all_tests.yml
@@ -164,12 +164,14 @@ jobs:
         with:
           auto-update-conda: true
           python-version: ${{ matrix.python-ver }}
+          channels: conda-forge
+          mamba-version: "*"
 
       - name: Install build dependencies
         run: |
           conda config --set always_yes yes --set changeps1 no
           conda info
-          conda install -c conda-forge "tox>=4"
+          mamba install -c conda-forge "tox>=4"
 
       - name: Conda reporting
         run: |
@@ -177,6 +179,7 @@ jobs:
           conda config --show-sources
           conda list --show-channel-urls
 
+      # NOTE tox installs packages from PyPI not conda-forge...
       - name: Run tox tests
         run: |
           tox -e ${{ matrix.test-tox-env }}
@@ -226,6 +229,7 @@ jobs:
           python-version: ${{ matrix.python-ver }}
           channels: conda-forge
           auto-activate-base: false
+          mamba-version: "*"
 
       - name: Install run dependencies
         run: |
diff --git a/.github/workflows/run_tests.yml b/.github/workflows/run_tests.yml
index 070de1a53..195f24937 100644
--- a/.github/workflows/run_tests.yml
+++ b/.github/workflows/run_tests.yml
@@ -138,12 +138,14 @@ jobs:
         with:
           auto-update-conda: true
           python-version: ${{ matrix.python-ver }}
+          channels: conda-forge
+          mamba-version: "*"
 
       - name: Install build dependencies
         run: |
           conda config --set always_yes yes --set changeps1 no
           conda info
-          conda install -c conda-forge "tox>=4"
+          mamba install -c conda-forge "tox>=4"
 
       - name: Conda reporting
         run: |
@@ -151,6 +153,7 @@ jobs:
           conda config --show-sources
           conda list --show-channel-urls
 
+      # NOTE tox installs packages from PyPI not conda-forge...
       - name: Run tox tests
         run: |
           tox -e ${{ matrix.test-tox-env }}
@@ -236,6 +239,7 @@ jobs:
           python-version: ${{ matrix.python-ver }}
           channels: conda-forge
           auto-activate-base: false
+          mamba-version: "*"
 
       - name: Install run dependencies
         run: |