Hello, this is my first post here, so I hope this is in the correct area. It seems like a fairly advanced question to me. I am not exactly new to keeping fish, but I have never found myself in quite the situation I am in right now. I will say, I did search around for an answer, but I did not run across anything conclusive. Here is my situation: I have a 47g (actual held volume) tank. It was originally intended to be a small tropical fish tank, populated by many small fish. It had Neons, zebra danios, black skirt tetras, a few pygmy cories, and a black kuhli loach. Everyone was pretty happy, for a while, then I started loosing fish, which will happen from time to time. Nothing seemed particularly sick, and the tank was well established at the time, so I attributed it to the general quality of chain-store breeding stock. Never the less, I like to wait a few weeks after die-offs before adding anything back in, and to do it slowly at that. I brought my zebra and neon schools back up to 5 members each, from two, to four, then to five over the space of a few weeks, with only one dead, of a new fish in the first 24 hours, which I attribute to moving stress. At the end of the original die-off I was left with a single black skirt, and my preferred LFS does not get them often, only about once every other month, so I have not been able to get him any same-species companions as of yet.. The store that I got my pygmys at has gone out of business, and so that group is stuck a 3. Now to my issue. I also had a 37g tank setup to house my Jewel Cichlid and pleco. The Jewel died, I believe of old age, although he had never been particularly healthy, often refusing to eat for up to two weeks at a time, ignoring food when given. The pleco on the other hand has always been healthy and had a healthy appetite while living with the Jewel for nearly six years. About a week after the Jewel died the tank began to leak rapidly and I was forced to move the pleco into the community tank.When I tore down the 37 I took it's bio-wheel filter and threw it in the other tank to keep the colonies in it alive, and add the extra filtration. After this move I plugged my numbers into the tank calculator I use, at AqAdvisor.com, and it says I am full. Now this calculator does use the fully grown max potential load for the fish you plug in, and tends to be conservative in the numbers used to help avoid overstocking. Now I have noticed that while he does not appear stressed or sick per se, my black skirt is seeming lonely. He is a schooling fish, alone in a tank of other schools, and tends to stick to a particular area of the tank around the one decoration. I am concerned that this "home-body" behavior may be due to lack of proper companionship. All my numbers for ammonia, nitrate and nitrite are near zero. I am not having issues with fish fighting for space or chasing each other out of areas, beyond the normal playing, and I have lots of places to hide. If I come across some black skirts does anyone think I will actually cause any over-stocking issues by adding a few of them? At the moment I will not add more than 4 of them, since the recommended minimum group is 5. Also, I am actively trying to find a new home for the pleco. Sorry for the long read, but I do appreciate any input.