Been medicating a fish with Triple Sulfa, conditioning the water with Prime, and for awhile, the ammonia level was down to zero. At the time, thought it was done cycling. Now all of a sudden, it is back up to .5 ppg. Is this normal at all?
Short answer is no. If the tank was cycled, then an ammonia spike would need to be caused by either a sudden increase in the amount of ammonia being produced in the tank (added fish, fish died and started decomposing, overfeeding, etc) OR by a sudden loss of established bacteria (removed/replaced all filter media, introduced untreated tap water, etc). The other possibility would be that the tank was not finished cycling to begin with. How long has it been set up? Has anything changed recently, such as added fish, etc? What are your nitrite and nitrate readings?
I do not think the medication should have caused a mini-cycle, but I have not used Triple Sulfa...perhaps someone else can speak to that.
Hmmmmm....can't find the nitrate/nitrite test thing .....but, he wasn't eating his medicated food and a lot of it was just going to the bottom for a few days. I ended up vacuuming the bottom part to gett all the food up one day.....could the vacuuming of the substrate be the cause?
It's possible, but in my opinion doubtful. Some of the good bacteria does grow in the substrate, and you can disturb it by vac'ing. Consequently, many of us will only vac a portion of the tank at a time...I do 1/2 of my tank each week. Having said that, I have, on rare occasion, vacumed my entire tank and not experienced any problems. The largest concentration of bacteria is normally in the filter media. In my experience, so long as that remains undisturbed, you can do a lot of things to the rest of the tank and still be ok.
I guess at this point I would monitor the water closely over the next few days to be sure that ammonia does not get any higher. If it does go higher, do a 50% water change to keep it from getting out of hand and hurting the fish. I would also be concerned about finding the nitrite test...if you are getting an ammonia spike, there is a real good chance you will be getting a corresponding nitrite spike in the near future.