Yes, you will need at least a 75 gallon to house your bichir later, but I suggest upwards of 100 if you want to keep him with tank mates. As adults--- larger south American cichlids,any of the larger fancy plecostomus types, and some of the bigger Longirostrus catfishes I have seen kept with them successfully.
All of the fish that successfully fit in a 10 gallon will successfully fit in his mouth, and even larger community fish like mollies just aren't really a good idea to add with something that is predatory--injury could occur. I say it's really best to keep him by himself.
