Brand new to growing, DWC, yellowish slime on tubes in tank

[Valentina]

You can fill some water bottles half way and
freeze them. Then put them in your rez to
get the temps down until you can get something better.
Have extras so you can swap them out.

I love these zero budget approaches. Nice one!

[imnice]

19c is sweet spot in dwc, but some silver bullet which prevents and cures possible root rot but and cleans all your equipment in the water, also as Bud states, ya need to get ya temps down fast, try ice packs and keep watch on the temps better a little too cool than too warm.
Imnice

[sixsixsix]

Not all slime on tubes in DWC is bad and not all bacteria in DWC is bad, on the contrary! Plants benefit from certain microbials.
If there is no floating big "chunks" inside and the slime is only on tubes and the roots are white, you have absolutely nothing to worry about. Good microbials are aerobic, which means they thrive in oxygen rich environment and if the system is not sterile, which almost never is, they will colonize sooner or later. I will never ever grow hydro again without adding bennies, I'll tell you that.