Hello there..I am not new to owning an aquarium but it has been awhile so please bare with me. I have a 55 gallon aquarium. We let it cycle for 3 weeks, before we added ANY fish..and when we did add the fish it was because the pet store guy said are water was good to add when I brought him the sample. We had only added a few guppies and a female betta. Everything was well and fine, and then our fish just kept dropping off like flies. We would get our water tested..everything fine...so we would replace them. But the cycle of replacing the fish kept going and going. Well then I finally got tired of having our little fishies die, so I switched pet stores. When I did, the new guy told me we had alot of ammonia in our water! So I bought a couple Seachem products.."Prime" and "Stability". After a couple water changes and the medicines, our ammonia was back to 0..but now I got Nitrates and Nitrites in the tank! Is this normal? Is there anything else I should do? Any feedback would help me! Thank you!