I've read several times that a calcium supplement is good for these crypts. What is a readily available source to add to tank water? How much?

Thanks,

Russ

CaSO4 works well, not much, perhaps 5ppm or so.
I do not think it's so much Ca as it is KH.

The plants do very well in very soft waters in both natural native systems as well as aquariums.

Regards,
Tom Barr

Calcium chloride (pool hardness increaser) also works well, this is what I use.