BTW guys the thick, black, contractor trash bags was "da bomb!"
Everything released so easily.
I built one using the original plug and I built one using a Tupperware type container and both released very easy. They aren't hard enough inside for me to see about either taking out the tupperware container or simply using it for the key holder, but it was easy to remove the 2 rocks and make room to build a 4th.
I tried vermiculite as most of the sand in one thinking that would lighten the weight of the finished product, but it's still a little heavy. The 4th one will have more foam board inside to help out, but I've run out of vermiculite so the last one will be built with straight sand.
The rocks are drying lighter than I originally thought. The color was spot on in the first 2 days, but it fades as it dries more.
I had begun to think I could just lightly spritz the exterior with some acid type concrete color but now I see I'll need more than just a spritz, but I'm still light years ahead of all the write ups by using color in the concrete.
What I've learned is that building the bigger rocks around the pond will be a snap.
And if not a snap then at least much easier than I was originally thinking. (and I don't want anyone reminding me of these words when I start the real project)
I do need to figure out the fill material because I don't want to use 100% mortar on something that big & thick, and how to seal the edges off. I may need to build a mortar plug and then build the form for the rest and fill it with debris.
I could build some of them hollow and use them to store things, if I could figure out how to get inside them, but as Scarlett said "That's another day."