Hi everyone. I am new to this forum. We have had a 55 gallon freshwater tank for the last 5 years which has always seemed healthy and fish thrived in. We decided to upgrade because some of our fish were outgrowing our 55 gallon. We acquired a 150 gallon tank about 3 weeks ago. Set everything up and started the fishless cycle using some media from our 55 gallon tank. We followed the fishless cycle over the last 2 weeks and tested daily using the API freshwater master test kit. Everything seemed to cycle the way it is supposed to (although it took longer than we would have liked 
). Finally 3 days ago our nitrites dropped and our nitrates started rising. We did a 50% water change and added ammonia to make sure it was indeed cycling. Ammonia and nitrites quickly dropped to 0 and nitrates held steady around 5 - 10 ppm.
Last night we decided it was time to move fish from the 55 gallon to the new tank. Got everyone moved - 1 bala shark 10 inches long, 1 angelfish 6 inches long, 1 suckerfish 13 inches long (told ya they were outgrowing the old tank), 6 black skirt tetras all about 1.5 inches long, 1 goldfish about 1.5 inches long, 1 neon tetra about 1 inch long and one Cory about 2 inches long. They all seemed happy in their new surroundings, swimming around nicely. We watched them through the evening and everyone seemed ok. We woke up this moring and had lost 2 black skirt tetras, the goldfish, the neon tetra and the cory. And the angelfish and one of the other black skirts aren't looking very good. I tested the water again and it is ammonia 0, nitrites 0 and nitrates 5. PH is 7.4 which is the same as the 55 gallon tank. I tested the 55 gallon tank which we had kept running through the night in case we needed to move fish back. That had been testing ammonia 0, nitrites 0 and nitrates 80 -160. Nitrates have alway run high despite water changes but the fish seemed to thrive in that tank none the less. This morning the 55 gallon tank tested ammonia 0, nitrites 5 and nitrates 160 which doesn't make sense. I couldn't move any fish back to that tank because of the nitrites being so high so we are keeping them in the new tank that is testing better. Temperature is running the same in both tanks. Anyone have any thoughts on what could be happening and suggestions on what we should do. We were going to add more fish tonight because we were concerned that with the larger tank there wouldn't be enough biofeed from the current fish to keep the tank healthy, but don't want to add more fish if we have so many dying. Any help would be appreciated. Thanks.
). Finally 3 days ago our nitrites dropped and our nitrates started rising. We did a 50% water change and added ammonia to make sure it was indeed cycling. Ammonia and nitrites quickly dropped to 0 and nitrates held steady around 5 - 10 ppm. Last night we decided it was time to move fish from the 55 gallon to the new tank. Got everyone moved - 1 bala shark 10 inches long, 1 angelfish 6 inches long, 1 suckerfish 13 inches long (told ya they were outgrowing the old tank), 6 black skirt tetras all about 1.5 inches long, 1 goldfish about 1.5 inches long, 1 neon tetra about 1 inch long and one Cory about 2 inches long. They all seemed happy in their new surroundings, swimming around nicely. We watched them through the evening and everyone seemed ok. We woke up this moring and had lost 2 black skirt tetras, the goldfish, the neon tetra and the cory. And the angelfish and one of the other black skirts aren't looking very good. I tested the water again and it is ammonia 0, nitrites 0 and nitrates 5. PH is 7.4 which is the same as the 55 gallon tank. I tested the 55 gallon tank which we had kept running through the night in case we needed to move fish back. That had been testing ammonia 0, nitrites 0 and nitrates 80 -160. Nitrates have alway run high despite water changes but the fish seemed to thrive in that tank none the less. This morning the 55 gallon tank tested ammonia 0, nitrites 5 and nitrates 160 which doesn't make sense. I couldn't move any fish back to that tank because of the nitrites being so high so we are keeping them in the new tank that is testing better. Temperature is running the same in both tanks. Anyone have any thoughts on what could be happening and suggestions on what we should do. We were going to add more fish tonight because we were concerned that with the larger tank there wouldn't be enough biofeed from the current fish to keep the tank healthy, but don't want to add more fish if we have so many dying. Any help would be appreciated. Thanks.
