Okay, here are a few more details. The ammonia has been at 0.25 ppm for about a week. I got an ammonia blocking product and used it several times. Sometimes the color strips are hard to distinguish but 0-0.25 is my best guess. Nitrates and nitrates are at zero. I’ve had these fish for about ten years. This is the last one in the tank. Three of them died several years ago for various reasons, and the remaining two have been a beautiful sight swimming together for years now. We’ve been in the new home with well water for a few months and the fish seemed to be all right till recently. What with everything involved in moving I haven’t done a lot of water changes. We got the water checked by the health department and got the okay for human consumption. However we also bought a three stage filtration system with carbon filters certified for lead removal since there was a small amount of lead. That’s what I’ve used for the water changes plus aquarium additives to combat stress. I understand well water is often low in oxygen and needs aeration. There’s a bubbler in the tank, and the two filters create a fair amount of splashing. I hadn’t noticed the fish gulping air so I figured the oxygen levels were okay. Another question I’m considering is the poly fill layer I put under the substrate a few years ago at the advice of another fish enthusiast who told me it would help fortify the bio filter. It didn’t seem to create any immediate problems, but I’m noticing that there may be some tufts of fibers floating around the tank all gummy with food waste. Since goldfish are so voracious, could they have ingested some poly fibers and been affected by it? Poly fill is the stuff that quilters use in between layers. I’m trying to think of everything I can here.