Well, took Addy's advice, got some of that PL Loctite gunk, used it at the top of my waterfall to direct the water to the next rock, worked great! Then water was trying to go under last rock before pond. Sat and pondered, ended up emptying the newly deepened pond in the bend of the waterfall. I threw the clear stuff into the pond, but the gunky stuff I was trying to dump over the south edge and with a south wind ... NOT fun! I wanted to rework the dirt under the liner before that last flat rock. Decided to pull the liner so it would overlap that big rock, so there would be no way the water can go under it on the back edge, although it could still go off on the sides. Anyhow, that worked well, refilled just the pool and water was flowing over last rock very well!
Bad news, though. I was able to get the ball valve working on my DIY filter, but I probably messed enough with it to break the seal on the outside, saw that it was loose yesterday. I thought I had originally used silicone, but it just peeled off. I thought silicone was supposed to be VERY hard to remove? Wondering if I used something else. I tried using the roofing goop to seal it and let it dry overnight. Started to fill the filter this morning and it is still leaking. So, had to scrap filling the filter and getting the waterfall running today. Have the filter laying over so the seal can dry. Will remove the silicone on the inside and then rough up the plastic before putting good layer of silicone on the inside and outside again, after I remove the black PL stuff, which is probably going to be a royal pain. Oh well. Live and learn. I suspect the seal on the inside was also compromised, and I should have done both at the same time..
Besides one fitting on my valve to the fountain that has a small leak and needs to be replaced, everything else seems to be in working order. Still need to put rocks back on the waterfall outer edges, but going to rethink how I want to do that as well, maybe using some of the flat pieces in with the rounder stones from UT (where my daughter lives). There's always next weekend, and soon the time will change and I'll have evenings to work on final touches, too!
Fish are doing great, still pretty slow moving, and although I put some slightly dirty water into their home today but it should be settled by tomorrow.