
I ended up getting some shale because I could deploy it quickly. Just a rinse and it's pretty much ready to put in. I built up the pile in the middle and made a small pile over where the loaches like to hide before.
Here is a close up

He's a happier loach now. After I put it in they were all worked up, digging and exploring. The large loach disappeared for a little while but he is coming back out and doing some sort of dance I've never seen. straight up to the top and back down in a vertical column. I don't know what it means but he able to hide.
Thanks for all the feedback. Let me know what you think.