Hi and welcome to the forum
What is the GH
(general hardness) and KH
(carbonate hardness) of your water supply?
This information can usually be obtained from your water supply company's website or by telephoning them. If they can't help you, take a glass full of tap water to the local pet shop and get them to test it for you. Write the results down (in numbers) when they do the tests. And ask them what the results are in (eg: ppm
, dGH, or something else).
Mollies need a GH
above 250ppm and a pH above 7.0. Your pH is fine but the GH
might be too low.
SWIM BLADDER ISSUES
There are no cures for swim bladder problems and true swim bladder problems are uncommon. So no more swim bladder treatments please.
If a fish floats up when it stops swimming, it might have a swim bladder issue or it might have air trapped in its intestine. To test this you stop feeding dry food for a week and feed frozen or live foods instead. If the problem stops after you remove dry food form the diet, then the issue was air in the fish's intestine.
If a fish sinks to the bottom when it stops swimming, then it has a swim bladder issue. There is no cure for this.
Sinking to the bottom is different from a fish swimming level or hovering around the bottom. Fish that don't feel well will sometimes sit on the bottom or hang out near the bottom of the aquarium, or up at the surface near a filter outlet gasping.
The fish in the picture looks skinny and could have worms and or gill flukes.
What does the fish's poop look like?
Is the fish still eating well?
You can normally treat gill flukes with salt, see directions below.
Intestinal worms can be treated with Flubendazole or Praziquantel for tapeworms, and Levamisole for thread/ round worms. I will post the deworming info below.
I would use salt first and if there's no improvement after a week with salt, maybe try treating the fish for thread worms.
You can add rock salt (often sold as aquarium salt), sea salt, or swimming pool salt 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.