You are still cycling then and should not add anymore livestock. Most inverts and fish are very intolerant of unstable water. Nitrites are very poisonous to life in general, even in low amounts.. You need to get the point where you have no ammonia, no nitrite, and only nitrates, which are then taken out of the water when you do water changes and generally clean the tank.
Any livestock you have now is at risk and any you add has a high chance of dying. Also, additional food sources like feed for current livestock, or the waste products of the animals themselves you have now are basically causing more ammonia and more nitrites, but your bacteria levels are not high enough and balanced enough to break it down quickly.
Keep testing your water weekly, and if you have a decent saltwater store (probably not petco!) have them test your water too to make sure your results match theirs. When you get to zero ammonia, zero nitrates you can get a clean up crew if you don't already have one, then add a fish. You have to add things slowly to the tank or you will just overload the bacteria again and have a minicycle, which could crash your tank and kill sensitive animals again.
