Water storage

68-72f is best to avoid shocking roots and still have good O2 levels. Also, helps avoid microbes growing if you avoid warmer temps. So, it's best if it can be outside the grow area. Until i start irrigating daily, i usually only fill my rez for 1 or 2 irrigations. If it takes 2-3 days between irrigations, the water just sits too long. If it's a lower level while sitting for days, it speeds up the fouling process, too. My nutes mix at 4 cents per gallon, so throwing out a few gallons each time doesn't bother me if it saves me the hassle of cleaning more often. Each to their own. Marijuana nutes are often 3-5x more expensive than that and often times well above 5x, too, for the people that really get suckered, lol. Once i get going, i keep about 4-5 days worth of water in the reservoir (~35-45 gallons as i ramp up). I'm using about 8 gallons per day once it warrants daily irrigations. So, after 3-4 irrigations i refill. This way it won't sit at less than 50%. My last irrigation before refill draws down below 50%, but it is immediately topped off with fresh water... then sometime in the next 24h i add the nutes. If you do top off, a water metere (+/-5% error) is a useful tool to have. attach to end of hose and you'll see how much you add each time to mix up right amount of nutes to add. You are probably fine with airbubbles at that size, but a power head is better at mixing and aeration of the reservoir. At low levels it might add some warmth, so don't over do it with a powerful one. I have a 55gallon barrel, so i have a larger power head, but that looks like maybe ~20 gallons? So you wouldn't need a beefy one. The smaller or mid-sized would be fine. I scrub that down when i clean the rez, too. I've found avoiding drawing down too low and leaving over night extends the time between needing to clean it. Adding 2/3rds to 3/4th top off helps keep it fresh for several weeks. If the water stays clear and no smell, in my experience that is good enough. Every 30-40 days i drain, clean and refill.