well thinking of little round balls in liters messes me up. and how big is a 6" net pot? i'd guess about a liter no more than two, but that's a rough estimate based on pictures. no where will tell me the size in liters or something comparable. so give me some math to do and i'll do it lol
Ah,like 10 time as much as you will need. I got one a year ago and used them on an 11 bucket 2 liter system(then tossed them)and now on a six BB system with 6" net pots and i still have two 5 gal buckets full and a few other type of buckets too.Maybe 20 times as much as i needed,but eventually i will use it.
Your 25 liter to 7 gal. conversion may work on the paper you use,BUT i just filled two 5 gal buckets with the new Hydroton i have yet to use and also have five 6" net pots filled with 3 foot plants growing out of them ATM,all came from the same 25 liter bag i opened new nearly one year ago.