hello. I am relatively new to fish keeping but from what I read you have made the same mistakes I did. You definately want to test your water daily untill your levels balance out, and continue to do 20-25% water changes daily until your levels balance out, they will not balance on out on thier own you need to continue daily water changes. Essentially you want ammonia and nitrite to be 0, nitrate to be less than 50 (you may want to double check with someone more experienced on the nitrate level, less than 50 is just what I read), and your pH to remain stable - roughly the same as your tap water). When you do your daily water exchanges you don't necessarly need to add anything to the tap water (in fact I would reccomend not to I have had fish die with in a few hours after adding water with dechloninators added). Essentially, if you let your water stand for 24 hours before adding it to the tank it will do the same thing as the chemical additives. Letting your water stand for 24 hours is easier, cheaper and in my opinion safer for your fish. Essentially get a container large enough to hold the amount of water you will be replacing fill it and let it sit for 24 hours. I have a 5 gallon tank so I know that 20-25% is roughly a Gallon of water so I have 4 - 1 gallon containers that I always keep full that way I know I will always have some water ready for the fish tank. Additionally may I recommend getting a liquid test kit, they are a little more expensive and a little more difficult to use but the results are much more accurate. The test strips I have found out are often inaccurate and can cause you a lot more trouble then they are worth due to the inaccuracy. I have an API master test kit (test ammonia, nitrate, nitrite, pH and High range pH) this should be all you need it was $30 from PetCo. However, you can find them cheaper at stores such as Walmart or on EBay. You can also get more expensive kits that have more tests but from everything I was told unless you are keeping live plants you don't really need the more expensive kit. My guess is that your since test strips don't test ammonia levels your ammonia is high and that is why your fish are dying. Since your tank is approximately 2 weeks old you are doing a Fish-in cycle (there is a great article on this forum regarding fish-in cycling). Once you get your tank cycled I was told that you still need to test your water weekly (in this case before a water change) and change 20-25% of the water weekly. Finally, when doing a fish-in cycle you want to use a hardy fish and not to many at first. I am using a zebra danios, just one in my 5 gallon tank. I am also 2 weeks in and so far he is doing fine. So keep in mind your more delicate fish, and possibly your hardy ones, may die using a fish in cycle. If all your fish have already died (and I hope that is not the case) you may want to start fresh with a fishless cycle (both the fish in and fishless cycle articles can be found on the fourm under "new to the hobby" then "Beginners Resource Center). Hope this helps.