[Kathyy]

^+1

My python extension never has tap water running through it so turned purple and black from the tank water. I coiled it up in a tub, wedged a small pump to one end and filled the tub with tap water plus several glugs of bleach. Even though I ran the pump for 24 hours the hose didn't get completely clean but it is just pink now, no purple or black.

My main hose is perfectly clean. It gets ~90 gallons of tap water run through when I refill the tank. I suspect rinsing the siphon with more tap and hanging to dry would keep the hoses clean without having to find a tub and figure out how to attach a pump to it.

 

[Kathyy]

I have a few small pumps laying around as I keep anything that works when I upgrade filters and tanks. I used the little pump that came with a 36" long SeaClear II aquarium I sold 12 years ago. A powerhead would work fine. A HOB filter might even work if the hose wasn't too long. It is just to move water through, doesn't need to be fast movement and it isn't pushing water up or anything.

The hose I cleaned is 20' long and dunking in bleach water didn't do a thing. You could try simply soaking and dipping and dumping water in the hose for as long as it takes if your hose is shorter though.