This is the best way to buy moss for the vivarium as it is dried and free from bugs or mold
New Zealand moss is getting difficult to obtain so recently we have switched suppliers & now stock the wafer rather then the chopped cube blocks.
The moss as seen in the photo is much more stringy then chopped moss but the process to activate is the same, just place the wafer into a tray or tub add about 1 ltr water.
Ok now you can add more or less water, some people like wetter others drier, but you really can't go wrong as any surplus water can simply be drained away or just squeezed out.
The photos show the amount after I added about 1.5 ltrs water, but it's really up to you, it is really magic to watch it expand.
The wafers are approx 48-50 grams