Fish Tank Fungus Problems

More fish problems – they’ve nearly all died!?

Last Sat I bought 6 minnows, a fantail and a black moor. The minnows all died within 4 days and the black moor yesterday, so there’s only the fantail left and it has a cloudy patch at the base of its dorsal fin. I’ve treated it with cotton wool and fungus treatment 2 days ago and have taken the filters out as instructed. My other two fantails which I’ve had for a couple of months seem to be healthy. I vacuum the tank weekly and change 20% of the water. Was it a bad batch of fish? They weren’t in the same tank in the shop or am I doing something wrong. A friend has had a minnow and a comet in a bowl for months and they seem to be doing just fine. If the new fish were diseased how can I be sure it won’t spread and what can I do to make sure the water and tank are disease free. I can’t seem to find any disease with this symptoms on any sites on fish keeping

Beginning to get a bit fed up with dying fish as we lost a black moor a couple of weeks ago for no obvious reason

There is an obvious reason. Is your aquarium more than 200 gallons? If not that is your reason. You need about fifty gallons per goldfish for good health and long lifespan. Your friend may have a minnow and a black moor in a bowl but they are not doing well; they just haven’t died yet. The largest cause of disease is overstocking followed by not quarantining new fish purchases. Now that you know what you are doing wrong you can adjust your stocking levels to suit your tank. If you would like help please feel free to contact me. Too many people leave this hobby for just this reason. I also recommend finding a local aquarist group. They can be a great source of information and help. Ask local fish stores as they usually know of one in your area.

Fungus detected on RTG fin