Excess mucous and damage to the tail, along with weight loss and death.
Excess mucous is caused by something in the water irritating the fish. It can be poor water quality, chemicals, or external protozoan parasites.
The excess mucous is mostly on the tail and that is probably from an injury to the tail.
How long does it take the fish to get skinny?
What does their poop look like?
If they get skinny over a course of months, then it's probably intestinal worms.
If they get skinny over a week or two it's usually an internal protozoan infection.
Fish getting skinny over time can also have gill flukes. Fortunately intestinal worms (tapeworm) and gill flukes can be treated with the same medication.
See following link for treating fish with stringy white poop. Section 2 is about internal protozoan infections and section 3 is about intestinal worms.
www.fishforums.net
You can add some salt and see if that helps. Use salt for 2 weeks and it will kill any external protozoan parasites like Costia, Chilodonella or Trichodina.
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SALT
You can add rock salt (often sold as aquarium salt), swimming pool salt, or any non iodised salt (sodium chloride) to the aquarium at the dose rate of 1 heaped tablespoon per 20 litres of water. If there is no improvement after 48 hours you can double that dose rate so there is 2 heaped tablespoons of salt per 20 litres.
If you only have livebearers (guppies, platies, swordtails, mollies), goldfish or rainbowfish in the tank you can double that dose rate, so you would add 2 heaped tablespoons per 20 litres and if there is no improvement after 48 hours, then increase it so there is a total of 4 heaped tablespoons of salt per 20 litres.
Keep the salt level like this for at least 2 weeks but no longer than 4 weeks otherwise kidney damage can occur. Kidney damage is more likely to occur in fish from soft water (tetras, Corydoras, angelfish, Bettas & gouramis, loaches) that are exposed to high levels of salt for an extended period of time, and is not an issue with livebearers, rainbowfish or other salt tolerant species.
The salt will not affect the beneficial filter bacteria but the higher dose rate (4 heaped tablespoons per 20 litres) will affect some plants and some snails. The lower dose rate (1-2 heaped tablespoons per 20 litres) will not affect fish, plants, shrimp or snails.
After you use salt and the fish have recovered, you do a 10% water change each day for a week using only fresh water that has been dechlorinated. Then do a 20% water change each day for a week. Then you can do bigger water changes after that. This dilutes the salt out of the tank slowly so it doesn't harm the fish.
If you do water changes while using salt, you need to treat the new water with salt before adding it to the tank. This will keep the salt level stable in the tank and minimise stress on the fish.
When you first add salt, add the salt to a small bucket of tank water and dissolve the salt. Then slowly pour the salt water into the tank near the filter outlet. Add the salt over a couple of minutes.
Excess mucous is caused by something in the water irritating the fish. It can be poor water quality, chemicals, or external protozoan parasites.
The excess mucous is mostly on the tail and that is probably from an injury to the tail.
How long does it take the fish to get skinny?
What does their poop look like?
If they get skinny over a course of months, then it's probably intestinal worms.
If they get skinny over a week or two it's usually an internal protozoan infection.
Fish getting skinny over time can also have gill flukes. Fortunately intestinal worms (tapeworm) and gill flukes can be treated with the same medication.
See following link for treating fish with stringy white poop. Section 2 is about internal protozoan infections and section 3 is about intestinal worms.
What to do if your fish has Stringy White Poop.
Fish do a stringy white poop for several reasons. 1) Internal Bacterial Infections causes the fish to stop eating, swell up like a balloon, breath heavily at the surface or near a filter outlet, do stringy white poop, and die within 24-48 hours of showing these symptoms. This cannot normally be...
www.fishforums.net
You can add some salt and see if that helps. Use salt for 2 weeks and it will kill any external protozoan parasites like Costia, Chilodonella or Trichodina.
-------------------
SALT
You can add rock salt (often sold as aquarium salt), swimming pool salt, or any non iodised salt (sodium chloride) to the aquarium at the dose rate of 1 heaped tablespoon per 20 litres of water. If there is no improvement after 48 hours you can double that dose rate so there is 2 heaped tablespoons of salt per 20 litres.
If you only have livebearers (guppies, platies, swordtails, mollies), goldfish or rainbowfish in the tank you can double that dose rate, so you would add 2 heaped tablespoons per 20 litres and if there is no improvement after 48 hours, then increase it so there is a total of 4 heaped tablespoons of salt per 20 litres.
Keep the salt level like this for at least 2 weeks but no longer than 4 weeks otherwise kidney damage can occur. Kidney damage is more likely to occur in fish from soft water (tetras, Corydoras, angelfish, Bettas & gouramis, loaches) that are exposed to high levels of salt for an extended period of time, and is not an issue with livebearers, rainbowfish or other salt tolerant species.
The salt will not affect the beneficial filter bacteria but the higher dose rate (4 heaped tablespoons per 20 litres) will affect some plants and some snails. The lower dose rate (1-2 heaped tablespoons per 20 litres) will not affect fish, plants, shrimp or snails.
After you use salt and the fish have recovered, you do a 10% water change each day for a week using only fresh water that has been dechlorinated. Then do a 20% water change each day for a week. Then you can do bigger water changes after that. This dilutes the salt out of the tank slowly so it doesn't harm the fish.
If you do water changes while using salt, you need to treat the new water with salt before adding it to the tank. This will keep the salt level stable in the tank and minimise stress on the fish.
When you first add salt, add the salt to a small bucket of tank water and dissolve the salt. Then slowly pour the salt water into the tank near the filter outlet. Add the salt over a couple of minutes.
