"I just started stuffing them into the substrate with this water change, so I haven't sucked them up, yet, lol. I just shoved it close to the Amazon, btw, almost under it, but not quite. Is that right?"
You can add the fert sticks in a radius around the plant that's as large as the leaf span.
"Ok, sweetheart, it's 150g, 5 gallon refills at a time. I do 10 of those and I'm one sore puppy. 17? Ugh. LOL I really need to figure out an automatic system, then I'd be able to do more of it, or more often."
Hehe, you use a 5 gallon bucket? OMG! Buy a good quality water hose and siphon it out. If you have a faucet nearby you can refill your tank very easily! Or you could use a waterbed attachment to your sink, or buy a python. If you go the water hose route, cheap water hoses will kink really bad, and only use it for your water changes.
There are a couple of sources of potassium. Seachem's potassium additive is far too weak. It would take almost 500mL per week! I use a brand called Hi-Yield "Muriate of Potash." It's essentially KCL. There is also another formula, K2SO4--potassium sulphate that will work also. These chemicals are produced by many different manufacturers, and are usually available at nurseries. A couple year's supply should run you less than $10.