I have one of those ubiquitous Brita water filter pitchers that sits on the kitchen counter in my house. About every month or so, I notice that it begins to develop a greenish tint, and sure enough closer examination reveals a tiny coating of algae, usually on the bottom of the pitcher. What gives? Admittedly, the pitcher is exposed to direct sunlight occasionally, but algae doesn’t spontaneously generate, it has to come from somewhere. Does the filter not remove it, or is it airborne and somehow works its way in through the pouring spout? Any ideas?
Keep it in the fridge.
That would solve the problem, but it does not answer the fundamental underlying question of where the algae is coming from.
I get this too, I vote for the spores (or whatever) being in the tap water and the algae can take hold because the filter removes the Chlorine that normally keeps it down.
I just wash the jug when it looks too icky.
Any remaining chlorine is gone after sitting in the light, too, facilitating algae growth. Also, if your water is slightly acidic and/or has a hint of nitrogen in it, then expect accelerated growth. Nitrogen finds its way into water supplies from home owner use of lawn and garden fertilizer, among other things. Green things love nitrogen.
BTW, ammonia delivers nitrogen. Don’t clean the pitchers with ammonia or ammonia based products, such as windex and other glass or multisurface cleaners.
(Do you have well water?)
Also, how often do you change the filter?