Hi, I've had an aquarium for 4/5 years now, but have a sudden issue with my fish.
We have/had 2 orandas, 6 amano shrimp in a 62l aquarium with a CF2 filter and an air stone.
Earlier this year in the hot weather we lost a fish to swim bladder problem, and 3 weeks ago we bought a new one to replace it. Each daughter has a fish each which they name, and love.
earlier this week i noticed they were both off their food. I tested the water - all fine, did my usual water change at the end of the week. Things worsened at the weekend with them both being lethargic. during a brief swimming stint i noticed that the bigger fish's tail was shredded at the end, so i headed down to Pets Corner and grabbed some fin rot treatment which went in Saturday evening.
Rather than getting any better, the bigger fish died last night, and the baby looks like it'll join sometime today. I have taken it out of the main tank into a quarantine aquarium as i saw one of the shrimp go for it, so I figured it was probably going to die anyway, at least it should do it in peace.
I have no idea what the issue is - can anyone shed any light? the water is fine, i've tested again this morning and all is within the green areas on the charts. Are the shrimp killing my fish?! I already have one very distraught daughter, and likely to have the other one the same after school today.
Sorry - I tried to reply earlier but the site went offline. Also sorry to read about this very sad situation - I also name and get attached to my fish, so I can only imagine the distress your young daughters are suffering. I do hope the baby fish is "hanging on" but it doesn't sound like it will have.
Although you mention "the water tested fine", what brand and type of test kits are you using, and what are/were the exact results? What may seem as fine may have some subtle differences that help make the diagnosis.
I think the crux of the problem is almost certainly the small tank (https://www.fishkeeping.co.uk/articles ... -size-life-expectancy.htm), coupled with a partial fish-in cycle once the new/replacement fish arrived. Essentially, once the previous fish died, the beneficial bacteria in the filter that processes the fishes' waste will have pared back to only process that of the one fish; once the new/replacement fish arrived, the filter would have been struggling to cope with the additional bioload. Careful monitoring of the water quality (ammonia, nitrite and nitrates) at least once a day would be required for the following couple of months, addressing the issue as per https://www.fishkeeping.co.uk/articles ... ammonia-nitrite-spike.htm
Does your filter have any carbon in it? If so, that would impede the effectiveness of the medication.
If, by any chance, the baby fish has died, and your daughters would like new fish, then I strongly suggest that *either* you purchase a larger tank suitable for goldfish and do a fishless cycle https://www.fishkeeping.co.uk/articles ... hless-cycling-article.htm, then stock once that is complete, *or* buy some fish more appropriate to the tank size such as male platies or male endlers, white cloud mountain minnows, or cherry barb tropical fish.