Bacteria and slime are normal in DWC water, the only problem I know of is Bacteria and slime stop up bubble stones quickly, buy more stones and the operational cost increases. The solution to that problem is “buy more bubblers.”
Fungi clean up dead rotting organic matter, are ubiquitous, they do not colonize nor attack healthy plants, healthy root systems or healthy bacterial colonies unless the roots systems and bacterial systems in the DWC are sick, dying, dead and decaying.
Fungi are opportunist, sick and dead roots present the ideal opportunity for fungus to colonize and thrive.
Do you believe that roots systems and bacterial systems begin to get sick, die and decay when DWC water temperature exceeds 72F? And that’s the justification for the chilled water and cost of water chillers?