I use two pumps from Atlas Scientific - one for a jar of base and one for a jar of acid. I have a sensor for PH so I can see in the live dashboard, and can click a button on the dashboard to disperse a set number of ml to the tank. I should have been clearer - PH is the one thing I didn't "close the loop on" because it'd be a little volatile. For instance when you first add nutrients to the water the PH drops steeply but stabilizes over hours or a day, I didn't want to respond too constantly to those changes. I should spend more time on this aspect though and maybe just have notifications for when it makes decisions.