We set up out tank on 12/24. Put fish in. Kept up with water changes and levels. Last Sunday, we got the nitrite levels coming up (finally) and the ammonia dropped. Checked again tuesday and Thursday. Same results: rising nitrite, ammonia at/near zero. Today, nitrite reads zero and ammonia has spiked back up to 4!! What??? My son broke our bubbler. Could that be an issue?