Reference reading if you have not already read it:
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=92639#Post92639In clean clear oligotrophic and some mesotrophic waters the DO will remain high enough to support trout below the thermocline. Northern temperate ponds are very rarely oligotrophic or mesotrophic. Most are euttrophic maybe slightly mesotrophic. Occassionaly you will find some mesotrophic as in the case of quarries or some deep gravel pits.
