Bread code liquid starter maintenance

Hi everyone. I am trying out Bread Code's liquid starter because supposedly it favors more lactic acid production over lower hydration starters. However, the video tutorial does not go over when I should feed the starter. With a regular 100% hydration starter I know that I should feed the starter when it doubles to triple in size. With a liquid starter there is no rise. I can see bubbles but nothing else. Has anyone tried this method with success? If not are there alternative methods to favor more lactic acid production? I have heard of people submerging stiff starters in liquid, and that might favor lactic acid more because the water will off the bacteria's access to oxygen, but I've never tried it. Thanks.