Default index cannot be removed

When Acquia search is enabled, a default index "Acquia Search Solr Index" is created and enabled. I don't want this index, as I have another index containing the data that needs to be searched, so I wish to disable and remove this default index.

While I can disable the index using the UI, I am unable to remove it (there is no "Delete" entry in the list of available actions). This may be because it is flagged as the "default" index, but I cannot find any way to make my other index the default.

In addition, even though I disable this index in line with recommended best practice of having only one index per search core, the index is re-enabled every time cron runs. Once again, this might be because it is flagged as the default index.