I overwinter my goldfish
in a 100gallon rubbermaid stock tank in my basement. I have done this for five years with no problem. I have it hooked up to a 5 gallon gravel homemade "bog" for filtration and always have great clarity and no issues. I also have a smaller tank with my "special needs" goldfish
that have been injured during the summer and I don't want them eaten by the others. Last Tuesday I did a water change and filter mini rinse (just to get the large gunk out) and had no problems. (I also have an umbrella palm in the tub for extra filtration) I had no problems until I went downstairs last night to check on them and most dead--float AND sunk on the bottom. No bloody gills, no signs of trauma. I immediately did a water and check and pH and nitrates were in normal parameters/no nitrates. The fish in the hospital tank which I also did a water change on were fine. The ONLY thing I can think of is that I trimmed the roots on the umbrella plant and maybe there was a toxin involved? I am heartbroke as all of these fish were born in my outdoor pond and some of them were about 12". Any ideas?? This morning I emptied the whole stock tank and rinsed it well and refilled it. I treated it with AmQuel and dechlorinator. Temperature was the same so I put the remaining fish back in but it doesn't look like they are going to make it either. The only other thing I can think of is we have had extremely cold weather here in Minnesota (-18) and wonder if the city changed chemicals in the tap water??
Thanks in advance--