I heard that they had very strong mixing algorithm. What mix algorithm did they use? Is there any service that uses the same or even stronger mixing algorithm?
Any service that uses the same security?
I don't know what algorithm Bitmixer was using but you may take a look at Chipmixer https://chipmixer.com/ and see if it's good your needs. It's a popular mixer and more now Bitmixer closed and they do not take any commission. There is a topic discussed here in the forum if you want to read more about https://bitcointalksearch.org/topic/ann-chipmixercom-bitcoin-mixer-bitcoin-tumbler-mixing-reinvented-1935098 and a blog article that you can find here https://themerkle.com/what-is-chipmixer/
here is another one you can check https://bitcointalksearch.org/topic/banned-mixer-fast-secure-and-reliable-bitcoin-mixer-since-2016-1484009