Is IELTS necessary for Dependants?

Hi

I got ACS and planning to apply for Australlian Immigration.
Can anybody tell me that my spouse also need to give IELTS as i am the principal applicant.

Thanks

i am filing for ACS assessment next week but my ielts is going to expire in nov next month . will it still be coinsidered or do i need to take out a letter from university showing the medium as english