I saw your post on another forum, which reminded me that I wanted to address one more issue - you said you would only turn the falls on intermittently. We have our pondless on a timer which turns off every night for 6 hours. I don't think you want to leave water standing in your reservoir for much longer than that. Standing water is known for several things - stagnation, which smells and breeding grounds for mosquitos... even under rocks. We had a garbage can filled with gravel that got rain water in it and the mosquitos were breeding in it under the gravel. So keeping that water moving on a regular basis is important.
Your milk crate idea is creative and I can't really think of a downside. Although you might find pulling them out is more of a pain than you might think. Our reservoir has a vault inside it that houses the pump so we only need to pull the lid off the vault to take the pump out. You would have to remove all your rocks every time you need to access the pump to keep them from falling in, right? I guess if you used larger rocks that might not be a big issue, but most pondless systems have smaller rocks or even gravel to give you that disappearing water look. And a milk crate might have holes that were too large - smaller rocks may fall in. Not the biggest deal, but something to consider when choosing your rocks for the basin.
Also remember that your construction needs to take into consideration the stream depth required to hold the volume of water you intend to have flowing. Sides that are too shallow will create constant water loss and frustration.
Just some things to think about.
Your milk crate idea is creative and I can't really think of a downside. Although you might find pulling them out is more of a pain than you might think. Our reservoir has a vault inside it that houses the pump so we only need to pull the lid off the vault to take the pump out. You would have to remove all your rocks every time you need to access the pump to keep them from falling in, right? I guess if you used larger rocks that might not be a big issue, but most pondless systems have smaller rocks or even gravel to give you that disappearing water look. And a milk crate might have holes that were too large - smaller rocks may fall in. Not the biggest deal, but something to consider when choosing your rocks for the basin.
Also remember that your construction needs to take into consideration the stream depth required to hold the volume of water you intend to have flowing. Sides that are too shallow will create constant water loss and frustration.
Just some things to think about.
