i don't know how to implement a stock system but if it were me i'd probably do something like this. If i had for example 10 springtail cultures ready for sale, i'd only list on the site that i had 5, that way if something happened i'd have backup. I'd make sure i always had a security stock on hand and never out too much at a time. Sell some, build stock, sell some, build stock.
Good luck with your business! i'm sure you guys will work it out hopefully
Customer service always comes first on my list when i look to deal with people. I usually buy all my supplies from Josh's because of the great service they have always provided me. They sent me the wrong type of heat mat once and next day ship the right one out to me and let me keep the wrong one they sent me. Online chat is always a bonus to have. Being able to talk to someone right then and there with your questions and get instant feedback is great. And they will give advice on anything from their products they sell to anything else you have questions about dealing with frogs