Zeer pot and growing Cyps

[Linus_Cello]

(Apologies for the cross-posting, not sure if this was a better sub-forum for my question in case anyone who grows outdoors uses a Zeer pot. Originally posted in the Cyp Alliance sub-forum)

Greetings and Salutations-
I'm new to the forum, and as best as I could, I couldn't find a thread on this subject, so I thought I would start this one.
I'm interested in growing cypripedium hybrids. With the hot weather we had in DC, my cyps could have used a "zeer pot" (especially before they were knocked over by my neighbor's cat while I was on vacation, and the person watering the garden failed to notice, so it dried up) (see gardensatposthill.com/website/Cypripedium%20overview.htm). Does anyone on the forum use zeer pots for growing cyps? If so, what would be the best sand to use? Is play sand ok, or should I use something that has less salt, like pool sand?
Also would it be better if each cyp that I'm growing in a pot have its own zeer pot, or could I get a big clay pot and put 3 cyps in it?
The varieties I'll be growing are Gisela, Ulla Silkens, and Lothar Pinkepank.
Thanks!