garden hose

Some of the cheapos have plasticizers that can harm the fish, according to the owner of a store I know. He used a new one to change water on a tank of Tangynikans that promptly died. Most of the rubber ones should be safe, or to be extra sure-get an RV hose-rated for human drinking water-usually white, I believe.
 
Yah, some garden hoses use a chemical that helps to keep the hoses "supple" and "bendable."


To quell any doubts, I suggest going to a Home Depot or something similar. Go into the plumbing section and get Food & Beverage grade hoses. They have clear and reinforced, which looks just like the hose that goes on a spray nozzle at a sink. They're pretty cheap too. I picked up about....20 feet for 6-7$.
 
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