diff --git a/pkg/obitools/obiconvert/sequence_reader.go b/pkg/obitools/obiconvert/sequence_reader.go
index 0b0071e..697a7b6 100644
--- a/pkg/obitools/obiconvert/sequence_reader.go
+++ b/pkg/obitools/obiconvert/sequence_reader.go
@@ -1,11 +1,12 @@
 package obiconvert
 
 import (
-	log "github.com/sirupsen/logrus"
 	"os"
 	"path/filepath"
 	"strings"
 
+	log "github.com/sirupsen/logrus"
+
 	"git.metabarcoding.org/lecasofts/go/obitools/pkg/obiformats"
 	"git.metabarcoding.org/lecasofts/go/obitools/pkg/obiiter"
 	"git.metabarcoding.org/lecasofts/go/obitools/pkg/obioptions"
@@ -136,7 +137,11 @@ func ReadBioSequencesBatch(filenames ...string) (obiiter.IBioSequenceBatch, erro
 		}
 
 		if len(others) > 0 {
-			iterator = iterator.Concat(others...)
+			if NoInputOrder() {
+				iterator = iterator.Pool(others...)
+			} else {
+				iterator = iterator.Concat(others...)
+			}
 		}
 
 	}