diff --git a/bin/taxref_reformat_sidle.sh b/bin/taxref_reformat_sidle.sh
index 48267f73..c1e7c3c5 100755
--- a/bin/taxref_reformat_sidle.sh
+++ b/bin/taxref_reformat_sidle.sh
@@ -1,19 +1,21 @@
 #!/bin/sh
 
+derep="$1"
+
 # Untar any tar file in the working directory
 tar xzf database.tar.gz
 
 # Greengenes 13_8
 if [ -d "gg_13_8_otus" ]; then
-    mv gg_13_8_otus/rep_set/99_otus.fasta gg_13_8_otus_rep_set_99_otus.seq.fasta
-    mv gg_13_8_otus/rep_set_aligned/99_otus.fasta gg_13_8_otus_rep_set_aligned_99_otus.alnseq.fasta
-    mv gg_13_8_otus/taxonomy/99_otu_taxonomy.txt gg_13_8_otus_taxonomy_99_otu_taxonomy.tax.txt
+    mv gg_13_8_otus/rep_set/${derep}_otus.fasta gg_13_8_otus_rep_set_${derep}_otus.seq.fasta
+    mv gg_13_8_otus/rep_set_aligned/${derep}_otus.fasta gg_13_8_otus_rep_set_aligned_${derep}_otus.alnseq.fasta
+    mv gg_13_8_otus/taxonomy/${derep}_otu_taxonomy.txt gg_13_8_otus_taxonomy_${derep}_otu_taxonomy.tax.txt
     # remove uncompressed folder
     rm -r gg_13_8_otus
 elif [ -d "SILVA_128_QIIME_release" ]; then
-    mv SILVA_128_QIIME_release/rep_set/rep_set_all/99/99_otus.fasta SILVA_128_QIIME_release_rep_set_all_99_otus.seq.fasta
-    gunzip -c /SILVA_128_QIIME_release/rep_set_aligned/99/99_otus_aligned.fasta.gz > SILVA_128_QIIME_release_rep_set_aligned_99_otus_aligned.alnseq.fasta
-    mv SILVA_128_QIIME_release/taxonomy/taxonomy_all/99/consensus_taxonomy_7_levels SILVA_128_QIIME_release_taxonomy_all_99_consensus_taxonomy_7_levels.tax.txt
+    mv SILVA_128_QIIME_release/rep_set/rep_set_all/${derep}/${derep}_otus.fasta SILVA_128_QIIME_release_rep_set_all_${derep}_otus.seq.fasta
+    gunzip -c /SILVA_128_QIIME_release/rep_set_aligned/${derep}/${derep}_otus_aligned.fasta.gz > SILVA_128_QIIME_release_rep_set_aligned_${derep}_otus_aligned.alnseq.fasta
+    mv SILVA_128_QIIME_release/taxonomy/taxonomy_all/${derep}/consensus_taxonomy_7_levels SILVA_128_QIIME_release_taxonomy_all_${derep}_consensus_taxonomy_7_levels.tax.txt
     # remove uncompressed folder
     rm -r SILVA_128_QIIME_release
 else
diff --git a/conf/ref_databases.config b/conf/ref_databases.config
index 7b702dad..2d11769e 100644
--- a/conf/ref_databases.config
+++ b/conf/ref_databases.config
@@ -524,5 +524,14 @@ params {
             fmtscript = "taxref_reformat_sidle.sh"
             taxlevels = "D,P,C,O,F,G,S"
         }
+        'greengenes88' {
+            title = "Greengenes - Version 13_8 - clustered at 88% similarity - for testing purposes only"
+            file = [ "ftp://greengenes.microbio.me/greengenes_release/gg_13_5/gg_13_8_otus.tar.gz" ]
+            tree_qza = [ "https://data.qiime2.org/2021.4/common/sepp-refs-gg-13-8.qza" ]
+            citation = "McDonald, D., Price, M., Goodrich, J. et al. An improved Greengenes taxonomy with explicit ranks for ecological and evolutionary analyses of bacteria and archaea. ISME J 6, 610–618 (2012). https://doi.org/10.1038/ismej.2011.139"
+            fmtscript = "taxref_reformat_sidle.sh"
+            taxlevels = "D,P,C,O,F,G,S"
+            derep = "88"
+        }
     }
 }
diff --git a/conf/test_multiregion.config b/conf/test_multiregion.config
index d320b192..1fc0fc9b 100644
--- a/conf/test_multiregion.config
+++ b/conf/test_multiregion.config
@@ -23,11 +23,12 @@ params {
     input = "https://raw.githubusercontent.com/nf-core/test-datasets/ampliseq/samplesheets/samplesheet_multiregion.tsv"
     metadata = "https://raw.githubusercontent.com/nf-core/test-datasets/ampliseq/samplesheets/metadata_multiregion.tsv"
     input_multiregion = "https://raw.githubusercontent.com/nf-core/test-datasets/ampliseq/samplesheets/regions_multiregion.tsv"
-    sidle_ref_taxonomy = "greengenes"
+    sidle_ref_taxonomy = "greengenes88"
 
     // Prevent default taxonomic classification
     skip_dada_taxonomy = true
 
-    //restrict ANCOM analysis to higher taxonomic levels
-    tax_agglom_max = 4
+    // Reduce runtimes
+    skip_alpha_rarefaction = true
+    tax_agglom_max = 3
 }
diff --git a/modules/local/format_taxonomy_sidle.nf b/modules/local/format_taxonomy_sidle.nf
index a6b909f5..72e55cd7 100644
--- a/modules/local/format_taxonomy_sidle.nf
+++ b/modules/local/format_taxonomy_sidle.nf
@@ -21,8 +21,9 @@ process FORMAT_TAXONOMY_SIDLE {
     task.ext.when == null || task.ext.when
 
     script:
+    def derep = params.sidle_ref_databases[params.sidle_ref_taxonomy]["derep"] ?: "99"
     """
-    ${params.sidle_ref_databases[params.sidle_ref_taxonomy]["fmtscript"]}
+    ${params.sidle_ref_databases[params.sidle_ref_taxonomy]["fmtscript"]} ${derep}
 
     #Giving out information
     echo -e "--sidle_ref_taxonomy: ${params.sidle_ref_taxonomy}\n" >ref_taxonomy.${suffix}.txt
diff --git a/nextflow_schema.json b/nextflow_schema.json
index 34f3ea1f..742f5cfc 100644
--- a/nextflow_schema.json
+++ b/nextflow_schema.json
@@ -508,7 +508,13 @@
                     "type": "string",
                     "help_text": "",
                     "description": "Name of supported database, and optionally also version number",
-                    "enum": ["silva", "silva=128", "greengenes", "greengenes=13_8"]
+                    "enum": [
+                        "silva",
+                        "silva=128",
+                        "greengenes",
+                        "greengenes=13_8",
+                        "greengenes88"
+                    ]
                 },
                 "sidle_ref_tax_custom": {
                     "type": "string",