
We have a 16,000 gallon backyard pond. Inhabitants are 10 large koi and 5,000,000,000 bluegill...ok, not really but 9 turned into "a lot more" quickly.

Not so much. Here is what has happened so far. I have kept a "log" of what I was doing so pardon the lingo...it's diary style:
MONDAY-WED:
I setup a 20L quarantine tank...only half full b/c that was all I could carry initially...I have since added 2 more gallons to make it 12 (am adjusting medicine quantities w/ gallonage increase) and will keep adding water as I bring it in from the pond and make it room temp.
He has been in there since Monday evening. I do not have a filter...only a bubbler.
I am testing the water daily and so far, nitrates/nitrites are very low and besides the water being a little hard (always is), it looks good.
The water is at room temp...around 67-68 degrees in our 100+ y/o house. LOL
I put in aquarium salt for freshwater fish.
THURS:
I am on my 4th day of treating with Marycyn. The initial prescribed treatment is 5 days.
He will not eat in the tank.
FRIDAY:
Well, he has gone from fin rot to now having fluffy stuff on his fins too.

Amazing what happens when you do your water tests CORRECTLY. The ammonia was at 2.0.
Added filter (hello idiot) and did a water change...15 minutes later...he starts swimming like a happy fish. 30 minutes later...he eats SIX worms!!! First time he has eaten all week!
I'm so excited I could cry. I'm such a girl. ROFLOL
Started him in TriSulpha drugs at advice of store for fungus on fins. Had to remove carbon from filter...TS kills all bacteria in tank.
SUNDAY:
Ammonia out of control again - not time to do a water change according to TriSulpha directions but have to do it anyway.
MONDAY:
Unhappy fish...unhappy owner...stupid pet store employee at generic pet store #1. TriSulpha doesn't treat what my guy has. He has saprolegnia....(or whatever it's called...wooly cottony stuff on his fins)....not body fungus, which is different.
Fin fungus is eating quickly and the fish is not well.
Go to pet store..pick up QuICK Cure...malachite green/formalin combo.
Pick up outrageously $$$ packet of Bio-Spira...some live bacteria that is supposed to eat ammonia.
Dumped in the bio-spira, put the filter back in trying to get ammonia back under control (at 2.0 on my test kit - Pond Master Liquid Test Kit).
TUESDAY:
12:30AM - Fish doing badly. Swimming w/ only one good fin and half of his one raggedy fin left on the right side. Scooting on the aquarium floor, mostly backward...then forward a little. Every now and then shaking like he is vibrating or something. Very odd!!!! Testing the ammonia for the 10000th time today...it's high again. 20% water change (one of a million I have done...also aquarium salt here and there and everywhere).
Put in QuICK cure b/c the fungus is aggressive and getting to the meat of the guy...red edges showing and he looks bad. Fish immediately looks like he is coughing...I freak out.
Scour the internet and find a remote reference that says that members of the Sunfish family (BLUEGILL) are particularly affected by malachite...it's toxic to them. I cuss.
Find another reference that says that you can treat sensitive fish at half strength.
Nothing like a 50% water change at 1am, eh?
I run out to the pond...check the temp...only about 6 degrees diff. between that water and tank water and pond water is testing zero ammonia. Refill 1/2 of tank w/ 8 gallons of tap water and 2 gallons from pond, tempered w/ warmer water from tap (yes, dechloring h20) to put more good bacteria into the tank.
SO...ALL OF THAT TO SAY...here we are now.
He is still cottony but since the water change and lower ammonia (now reading .5), he looks better...calm..breathing right...etc.
What do I do now? My .10 bluegill is now $70.10. LOL I'm not giving him up w/o a fight.
Currently:
20L tank full
Filter on but carbon out
Aerator
50% (a little less) treatment of QuICK Cure
Aquarium salt
Mega cottony fins
Fungus starting to eat into the flesh attaching the fins to the body
Don't know if I should get the antibiotics back in the water too or not...?
Will I need another 50% treatment of quick cure...if so...when?
I'm not even sure if I just leave the quick cure in the water or if i do a water change or what.
FOR THOSE OF YOU WHO MADE IT THRU THIS MESS...Thank you. LOL
I love this little guy and would really appreciate your help asap!
Andrea