I recently became the owner of a couple County Fair goldfish (thanks to my son lol) 7/13/15. With that being said I decided to get myself a 10 gallon tank 7/15/15. With the purchase of said tank I bought 2 glofish 7/15, 2 swordtails 7/15, and a birstle nose pleco 7/17. Unfortunately the 1 goldfish died a couple days after we borught them home.(we new this would happen as fair fish don't usually last long). The second goldfish died sometime early this morning 7/26. Both my swordtails died as well, one and then the other within a week of bringing them home 7/20 & 7/23. I did some research as most people would do being new to the aquarium world. I found I needed to test my water so I bought a water testing kit. Upon testing my Ph was around 7.5-7.6, nitrite was 0.25, nitrate 0 and Ammonia was through the roof so I did a complete water change after I tested my tap water (we have a well, not city water). Tap water turned out fine so I did the complete water change, and gave my tank a good cleaning. I bought 2 more swordtails 7/23 and 2 more glofish. One swordtail died today as well 7/26. The other swordtail that is left is spending a lot of time on the bottom but then will swim around like crazy for a bit and then go to the bottom again. the 4 glofish and the pleco are doing great. Finally to my question sorry for this being so long but wanted give as much info as I could. Am I buying sick fish, is there something going on that I am not aware of, or is this typical behavior for swords? I also have a bubble stone bar, a nice rock formation type hiding place and 2 fake plants for hiding. The only fish that I have bought from a big chain store (petco) is the pleco, all others have been from a local pet store, Any help is greatly appreciated.