I just acquired a Goldfish - Carassius auratus, and am using a 3.5 gallon container w/large gravel, a whisper filter, and 2 small plants (plastic). The fish seems real happy, he is 2" (body 1", tail 1"). Will the 3.5 gal be sufficient for this fish, at least for a little while? If so, you think he'd like some company in there, or is it too cramped already?