Citric Acid Solution: Mold after sitting?

[rhastareefer]

I understand you can MAKE citric acid by feeding starch to black mold (yummy!). However, I'm confused as I've heard many that use citric acid to clean pumps/power heads say that you can save and reuse your citric acid solution over time. I just pulled mine out of storage and found what looks to be a couple different types of mold growing fairly prolifically in the tub. Is this stuff safe to use for powerhead cleaning? Is it even safe? Throw it out and mix up a new batch or maybe add some extra citric acid powder to it? I'm using @Bulk Reef Supply 's product. Thanks for the feedback! Hopefully I can learn something :)

 

[ludnix]

I would toss moldy water. Even if there's a little acid left in the water I would be concerned about it not being a great medium for cleaning your equipment and potential health hazard for your self. I think in the future you could try pH testing the acid solution after you mix it and when you're done cleaning your equipment. Then you would have a nice base line for how much acid is left for reuse. I would expect the pH to start low and increase as it reacts with the various things you are cleaning off your equipment.