Last grow, particularily during the bloom phase, I had a lot of slimy stuff in the reservoir and controller when I cleaned out the system every week. Someone said that this was a result of using phosphoric acid based PH Down. Because the solution water is already saturated with phosphorus, the phosphorus dissolved in the water that comes into immediate contact with the phosphoric acid precipitates out into the solution. This is because the solution around the PH DOwn becomes overly saturated with phosphorus. It has nowhere to go so it becomes a solid. This leads to the slimy coating that you sometimes find inside the reservoir and on lines, etc, and in the controller.
This crop I started using Eco Grows brand of PH Down which uses some other sort of acid to knock the PH down and lo and behold, no more slimy crap in the system.
Now when I change out the reservoir it is almost spotlessly clean and I barely have to wipe things down. The difference is stunning and it saves me a lot of work every week.
Perhaps if you used a different brand and type of PH Down you would not have to worry about crap in your hoses. Just a thought.
http://www.horticulturesource.com/product_info.php?products_id=6140
