Optimizing Indices

I'm trying to do some index optimization by reducing the amount of replicas after an index really shouldn't be written to anymore. Following this link.

my curl statement looks like below, going after a distinct index called "logstash-syslog-2016.09.20"

I execute the following statement:

curl -XPOST 'rfdesmstr:9200/logstash-syslog-2016.09.20/_settings' -d '{ "number_of_replicas": 0 }'

I get this in return

{"error":{"root_cause":[{"type":"invalid_type_name_exception","reason":"Document mapping type name can't start with ''"}],"type":"invalid_type_name_exception","reason":"Document mapping type name can't start with ''"},"status":400}

Tried with sense as well and get the same result. Any ideas as to what I'm doing wrong?

curl -XPUT localhost:9200/INDEXNAME/_settings -d '{ "index" : { "number_of_replicas" : 0 } }'

If it will be something you do regularly, Curator has a Replicas action, as well as forceMerge and many others.