What medication(s) do you use for quarantine tanks?
For fish lice and anchor worms, dimilin X. For external parasites, Microbe Lift Broad Spectrum Disease Treatment (Malachite Green + formaldehyde based), or potassium permanganate, or salt. For internal, usually praziquantel and metronidazole, or fenbendazole. Also Epsom salt.
The RTC stopped feeding today. He hasn't been going to the top of the tank at all, he's only staying under the bridge decoration inside the tank. The only changes I made to the tank were removing the marbles, and two pieces of decor. No new symptoms, no fin rot, slime coat, or anything. His coloration looks great. I've only tried to feed a pellet once. Will try again later.
Is this a result of stress, or is his condition getting worse?
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Update, he's roaming around the bottom of the tank, whenever he approaches the pellet, he smells it and looks interested and then turns away and then keeps swimming around the bottom. Very rarely, it looks like he'll start "gulping", opening his mouth fully and closing it really quickly. I know it's not a result of low oxygen, the tank is oxygenated enough.
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Scratch all the former, he's just started "bumping" the surface of the water for unknown reason. He's staying at the top now.
What is going on with my fish?!?
IDK mate. It is not always possible to know, we can only try our best. Sounds like he is getting worse, losing appetite is a biggie. Fish yawn for various reasons, one of these is to help move the food along the intestines.
What you describe may also be an attempt to "blow" the gills. Since he is going to the top, I think his gills might be affected. He is not getting enough oxygen, probably. Could be gill flukes. These have a known treatment. Gill fluke infestation doesn't occur for no reason either. The fish is most usually somehow stressed too much, most usually through ammonia-laced water, which weakens their immune system, which then allows for the parasite to overtake.
Even if the parasite is killed but the root cause, ammonia in this example, not addressed, the disease will come back or something else will pop up.
At 1.5" RTCs or any fish are still pretty vulnerable.
Perhaps both your little RTCs or one of them came with some latent disease or pathogen, which is affecting them now but short of a pathology lab test, we won't know most likely. In 99% cases when people turn to medicine, it turns out a fish needed only pristine water and absence of stress to recover on its own.
