For the past year or so I was down to just one goldfish (Penny) and a BN pleco in my 55. I was so busy with other things and also waiting to see if there was a persistant issue in my tank after losing fish last year, that I never added more fish. The new fish bug finally bit around Christmas and I added Darwin.
So that puts me at 3 fish (BN included) in a 55 gallon, with an Aquaclear 110 (500 gph) and a Rena filstar XP 4 (450 gph), along with java fern and 2 anubias.
I cannot believe how well this system is working for me. I missed a water change this week and it made no (measurable) difference. I don't think I'll be adding any more fish. I also like the way the tank looks with just a few fish in it
I'm by no means trying to sound 'preachy' here at all, there's nothing wrong with fully stocking a tank, but I think after years of doing so and struggling to keep up with water changes, ect., this is the way for me. I'm so much more busy than I used to be with my career that I want the hobby to be relaxing, not stressful. I am one happy fish keeper right now