Please bear with me.

There is some very interesting information in this thread on temperature drop via evaporative cooling in degassing columns:
"Some big trout pics down memory lane"
This correlates with information on the web about small "bong coolers" for computers and diy swimming pool coolers for people in Texas.

I live in SW Washington near Portland and have a small garden pond that is 50 x 35ft by about 6ft deep. It's not a simple shoebox shape and I estimate the volume around 30k gallons. I have about biofilter/bog arrangement that uses 22 tons of pea gravel and use airlift pumps to circulate the water through the bog. There is no power at the pond, but I can plumb water or an airline without issue. I would like to plant a few trout (just for amusement). West of the Cascades we don't have major freezing issues but summer daytime temps can go up to where it would make Trout difficult without a lot of incoming cold water
However, given the relatively small volume of water, some sort of DIY cooling tower pumping a some reasonable fraction of the total volume per day, may be able to keep the temps down sufficiently. To recap the bucket based degassing column in the referenced thread dropped the water temp by 7F at 8gpm. This was achieved by evaporative cooling in ambient air temp of 72F.

I assume that a fountain would offer similar benefits and would not require a structure. I think I would want something in the 20 gpm range...
Does anyone have any relevant information or experience they could share?
Any ideas on how best to do this with solar?

with thanks
Beardy