They are safe. I got the regular size (5 of them) and have had them for months now. Still very healthy and all inhabitants.
In fact the ones I got were from the same seller. Good stuff. These are the ones I got. I have them in both my 60 gallon and 10 gallon planted tanks.
https://www.amazon.com/gp/product/B00LVRRROS/ref=oh_aui_detailpage_o08_s00?ie=UTF8&psc=1
In fact the ones I got were from the same seller. Good stuff. These are the ones I got. I have them in both my 60 gallon and 10 gallon planted tanks.
https://www.amazon.com/gp/product/B00LVRRROS/ref=oh_aui_detailpage_o08_s00?ie=UTF8&psc=1