I know this is kind of cliche, but quarantine. Any time I add a fish to my display tank, it has been quarantined for 2 weeks, more if there appears to be problems or the fish is in distress for some reason.
Qt helps in a lot of ways:
1. You can catch a pathogen on the fish that may not be visible at the time of purchase, but shows itself a few days later.....then treat accordingly.
2. You don't compromise the rest of your healthy stock with the potential of introducing a disease that can, possiby never be removed, only to lay dormant until a stressed host presents itself--slime reduction.
3. You can monitor the fish up close and target feed making sure he gets nice and fat and used to the food you feed the rest.
A QT Tank need not be a large investment. It can be as simple as a 10 gallon tank, with a 50 watt heater and air stone near a window (for lighting) in a secluded part of the house. Make sure TO NEVER CROSS CONTAMINATE THE DISPLAY TANK with any items used on the QT--ie siphon or fish net.
Now, after 3 months, unfortunatly, you are left with a pathogen in your tank and want to go back to the lfs
to put some more dough in their pocket---not trying to sound negative, but it's the reality of the situation. Your temperature is a bit on the highside. I like 78-79 degrees for a lot of reasons, most important being that O2
is depleted faster in sea water the higher the temp is raised. Less O2
, the more a fish has to labor, and the more stress is endured, and the lower the immunity to the pathogen.
I would absolutely hold off adding anything to the tank, until you are certain that ALL inhabitants are thriving and the new arrival has been quarantined for a period of 3 weeks. Step back from the situation before wading deeper into the darkness, if you know what I mean. In my personal experience, I have NEVER trusted the advice of any LFS
worker or owner. I read as much as I can and try to learn from experience in simple trial and error over the years.
loves to sell you fish, under most any circumstance
If I were you, this is what I would do:
1. Lower the temp.
2. Make sure I had proper O2
exchange at the surface of the tank directing the power head up
3. Set up a small QT tank for 30 dollars
4. Use the tank water to fill the QT tank
5. Replace the water from the DT tank with fresh mix that has been aerated for 24 hours--there's your water change
6. Remove the Royal Gramma and place him in the QT....give him a piece of PVC
to hide in. He will appreciate it---no rock, sand or gravel in the QT
7. Monitor all fish for the next 4 weeks, adding NOTHING
8. If symptoms appear on the Royal Gramma, treat with proper meds to erradicate the pathogen
9. After the last visible sign of sickness on the Royal Gramma, give him another 4 weeks of QT
10. Assuming all other inhabitants in the DT are doing well at this time, add the Royal Gramma back to the DT
11. Go buy another fish and QT for 2-3 weeks
I know none of this is what you want to hear, but it would be my strategy to turn things around.