Do you have any pics of your pondVik has been in the trenches longer than I have, but I had a pond similar.
Mine was roughly 10' x 4' x 4' if I remember correctly. Made it out of cinder blocks and lined the inside.I had a bigger rtc in there at one point along with some wolves and a silver aro. I had to keep the top covered or the aro would go flying.
Filtration was the biggest pia. I eventually switched to the ultima types over diy barrel koi type. I ran a small dehumidifier and had an exhaust fan ran outside.
I'll be honest I think the rtc needed more room than the 4' width.