I've heard HOBs should be cleaned weekly or they start to become nitrate factories.
Distilled is what you want. Im not sure Spring water has any RODI
in its processing. In my grocery stores, distilled is usually about a buck a gallon. The big dispensers where you bring your own containers are usually about 25 cents a gallon. They are outside most of my local gas stations and most grocery stores. That is what I use and I've had minimal algae. I try to get my water close to when they have been serviced.