I have a 20-gallon tank that has 6 lemon tetras, 5 harlequin/porkchop rasboras, 1 synodontis lucipinnis, and 1 lone serpae tetra (there used to be more but the school slowly dwindled as the years went by). I used to have a bristlenose pleco but unfortunately, it passed away a couple of days ago. A always felt bad that I only had one synodontis lucipinnis because I now know that they are a schooling fish but when I got it the people at my fish store didn't tell me that and that was before I knew to research about fish I wanted to get. Long story short, now that my pleco has passed away could I get 2 more synodontis lucipinnis for my tank, or would that cause it to be overstocked? Thanks in advance.