Those drumms are always shaded there. Im sure if the water temps dont go over 75-80 they'll be alright. The pond filter I found is rated for 1500 gallons
Maybe 6-8 week water changes
The ammo-lok can be had at any pet store and instantly neutralizes ammonia into non-toxic form.
The blue barrell has a bonze thru-hull and transom plug, but the ball vavle is much better. It was $4 at HD.
The only trouble with the black drums is you cant see the eels in em w/o a light shining in.
I may try hanging a black eel bag in the drum