Can it happens because I feed him and 10 of his tank mates 10 pellets every other day? @Colin_TIt looks skinny, has a curved back and clamped fins. Probable cause, gill flukes and intestinal worms.
Check the water quality for ammonia, nitrite, nitrate, pH and GH.
Add some salt and deworm the fish.
You can add rock salt (often sold as aquarium salt), sea salt or swimming pool salt to the aquarium at the dose rate of 2 heaped tablespoon per 20 litres of water.
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 4 heaped tablespoons 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, 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 will affect some plants. The lower dose rate will not affect plants.
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.
Intestinal Worms like tapeworm and threadworms cause the fish to lose weight, continue eating and swimming normally, do a stringy white poop. Fish can do this for months and not be too badly affected. In some cases, fish with bad worm infestation will actually gain weight and get fat and look like a pregnant guppy. This is due to the huge number of worms inside the fish.
Livebearers like guppies, mollies, swordtails & platies are regularly infected with gill flukes and intestinal worms. If the fish are still eating well, then worms is the most likely cause.
You can use Praziquantel to treat tapeworm and gill flukes. And Levamisole to treat thread/ round worms. If you can't find these medications, look for Flubendazole, which treats both lots of worms.
Remove carbon from filters before treatment and increase aeration/ surface turbulence to maximise oxygen levels in the water.
You treat the fish once a week for 4 weeks. The first treatment will kill any worms in the fish. The second, third and forth treatments kill any baby worms that hatch from eggs inside the fish's digestive tract.
Treat every fish tank in the house at the same time to prevent cross contamination.
You do a 75% water change and complete gravel clean 24-48 hours after treatment. Clean the filter 24 hours after treatment too.
Do not use the 2 medications together. If you want to treat both medications in a short space of time, use Praziquantel on day one. Do a 75% water change and gravel clean the substrate on day 2 & 3. Treat the tank with Levamisole on day 4 and do a 75% water change and gravel clean on day 5, 6 & 7 and then start with Praziquantel again on day 8.
The water changes will remove most of the medication so you don't overdose the fish the next time you treat them. The gravel cleaning will suck out any worms and eggs that have been expelled by the fish. Repeating the treatment for 3-4 doses at weekly intervals will kill any worms that hatch from eggs. At the end of the treatment you will have healthier fish.
How do I tell if fish have gill flukes? Also whats the dose for the medication? Thanks again Colin.No that is not from only being fed once every two days.
Livebearers always have gill flukes and intestinal worms and that fish is emaciated and needs salt and dewormer.
What about the dose rate how much med to add?Fish infected with gill flukes will usually be skinny, pale, and have flared gills.
Basically any livebearer from Asia should be treated for worms and gill flukes as soon as you get them. And any fish that has been in a tank with livebearers, or in a tank that has had livebearers in, should also be treated for gill flukes and intestinal worms.
Gill flukes are easy to treat with salt or a tapeworm medication. I use salt and deworming medications because the salt also kills a lot of external protozoans and some bacterial and fungal infections.
I cant find any, all of the store was closed. I might have to order from amazon, can they wait 2 or 3 days? Also Colin does this discus skinny too? He dont eat for the past 3 days.Praziquantel is used to treat tapeworm in dogs and cats. It is also made by a couple of companies to use on fish for gill flukes and tapeworm.
Levamisole is used to treat livestock for round/ thread worms. It is available in 3 different dose rates (cattle, sheep and poultry). Cattle is the strongest concentration, sheep is the middle concentration, poultry has the lowest concentration.
It's also available in powder and liquid forms. I have only used the liquid form and no longer have my notes about the dose rates.
The following link has information about the dose rates for Levamisole Hydrochloride.