Despite you have this ability to create channels in types of Public or Private, you are able to send your public channel ID or its username to a private channel in order that other members join it easily as well. The only rule you have to follow is to use @ in your message.
In the Web version of iGap there are many features as in other versions. One of the most important of them is to have your own room as a channel and even in public. It means that you do not need to add members to increase the number, all iGap users can join it easily and use the shared media. Do not forget, your public channel needs a username or an ID, so others can join it by clicking.