The names you called them are basically the names stores give them. You have what looks to be albino senegalus and a normal senegalus. On here they're typically referred to as "sens" or "albino sens". The tank you have them in now would be about the smallest you could fit them in. If you have the space, time, and money I would recommend upgrading to a 75g in the future. While sens usually tend to be the smallest of all Polypterus they are the most active so a large swimming space is a good thing to have. As far as tank mates, there's a couple general guidelines. 1) can the bichir fit this tank mate in its mouth? If so then it might eventually become food. 2) will this tank mate bully or harass the bichir? If so then it may end up stressing the bichir to death. 3) Can the tank mates eat the bichir? If so then it's an obvious no. If you follow those guidelines it's pretty easy to choose tank mates. It may require some research on your part to see if the fish you want to try and get will fit te requirements or not, but it's nothing that a 5 minute Google search can't help with. I would suggest putting a list of fish you want on a notepad or something, then sit down and research them a at once and mark them off as they don't fit, or circle them if they do.
