FnC if you have spring water flowing into your pond all the time, a syphon pipe can't hurt you. I don't care if you put in on the bottom or the top. DO the MATH. How much water do your receive each hour, day, week. ect. and how much water does your pond hold? Getting rid of bottom water is never a bad thing. I can find no data that says getting rid of the worst water in your pond is a bad thing, so stop complaining about having to deel with so much water, put in a syphon pipe and be happy. Mine is located 4-5 feet off the bottom but I believe you can put one as close as 2-3 feet from the bottom without having any adverse affects (sucking up mud, ect.).
If you are worried about temperature, remember when water gets to about 39 degrees F it becomes less dense and floats. If the spring water is warmer than that, it will try to sink and mix.
Don't make me get out the zeroith law of thermodynamics on you!!! Just be happy you have to deal with that much nice clean new water, there are a lot of people here that would love to have that problem.
