1. It is not placed horizontally
2. There is a minimum water level in the pipe, which will not let all the water flow out, but only let the excess water overflow.
I am wanting to use this outdoors with a 100 gallon fish pond, but I am think this may heat up the water too much as it travels through the pipes. Does it heat up the water a lot as it is pumped through the system?
According to the product description, the hydroponic grow system is suitable for both indoor and outdoor use. The dark PVC pipes are designed to prevent sun exposure while allowing the system to be used outdoors for a long time.