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DoubleDDsNuggs
what are you using your airstones for brewing ? if so I would suggest separate airstones for brewing and just for water.. they shouldn't be slimy if their just in regular water.
I use them to brew the teas and I place them in clean water while I'm feeding. Then I dump some bleach in to clean and soak. They have brown slime covering them after 8 hours brewing. I had rot in my hydro too. Maybe that's why they're still dirty despite bleaching. I heard you're supposed to use muratic acid.