Looks good.
One additional thing I would personally do is drill lots more holes in the ends of the barrels, and even between where the tubes are. 3/4 to 1 1/2 in diameter, to give lots of places for very small fish to dart in and out of.
Without enough holes, I would doubt the water inside the barrel will have much oxygen in it. More holes will let more water flow potential and light and more likely small fish utilize more than just the outer surface of the barrel.
I don't know this to be the case, just what I would surmise. I tried to drill lots and lots of holes in all the plastic stuff I put in the water. I even drilled holes about every foot or two in the black plastic 1" or 1 1/4" pipe that is similar to the black pipe you are using. I thought this would allow the inner part of the tubing to be more utilized (by tiny fish) rather than only the outer part. I tried to make things look like Swiss cheese as much as my hand and arm would stand running the drill.
Just my ideas and what I did.
These work great drilling holes in sheet plastic The small one I drilled holes all the way through the tubing (small hole on opposite side and larger hole on entry side at same time). The big one for drilling holes in barrels and the like.
You have some holes and slots, I personally would just put a lot more, even if they are just smaller holes with a drill bit. A wood spade bit works ok too, but you have to be more careful when going through the last little bit. The step drills work super.
