wmsky, welcome to AA!
Off the top of my head, I'm not sure what the exact resistance range is on the pot I used. I know the top end is 10k, but I'm not sure about the bottom end. I grabbed the first pot I saw with the 10k upper range because I wanted to finish the project and I intend it to be temporary.
Looking at the schematic again, I see your confusion. With a 1k-10k pot, you lose a bit of the lower end adjustment compared to the 0-10k pot. I wasn't really concerned with low-end adjustability since my goal was a high-light tank. I wired the pot so it's in the 10k position when the the detent clicks, so I know when I've got max current and the knob won't turn with an accidental touch.
Tank update: I think I scored big on Craigslist yesterday. I purchases a pair of 20lb CO2
cylinders for $35. One still has something in it too, but I don't know how much. The bad news is I think both tanks are out of hydrotest date. I have to do some more research. One tank is definitely aluminum, the other might be, but I didn't find any obvious markings when I looked the bottle over.
I'm hoping to see if my free CO2
regulator is in working order tonight, but it might have to wait for the weekend. The solenoid clicks when you plug it in, but I don't know about the actual regulator. If the regulator works, I'm a small powerhead and drop checker away from the high-tech CO2
system I swore I'd never get when I started with plants.