Are the bubbles coming from the maxi-jet - there is an air tube attached to the maxi with an adjustable baffle, either close it a little or remove the airtube all togather. If not then was the water sitting un-circulated - if so the 02 will dissolve, get cloudy looking, then clear with no bubbles.
Algae - H20, Protiens/Ammino acids, Sunlight or immitated. Nuissance Algae can come from all kinds of sources from an abundance of silicates to high nitates or high phosphates which can be from tapwater. However, because phosphates are a naturally occuring byproduct of decomposition they can originate in the tank due to overstocking, over feeding, or an immature bio-system - R/O water or not. Good thing they make phos-reactors to remove it as well as the math ladden chemistry Vodka/Carbon dosing methods and/or simple refrigium tech.
If I was gonna use R/O water I'd get salt specifically designed for R/O water that contains the trace elements lost in the purifiying process