All fish have a thin layer of mucous over their body. It is the first line of defence against diseases. If the fish is stressed from something (usually poor water quality), they produce more mucous and can develop a cream or white film over their body and fins. Air bubbles will stick to fish if they have excess mucous.
Have you test the water quality for ammonia, nitrite, nitrate & pH?
If yes, what are the results in numbers?
How often do you do water changes and how much water do you replace?
Do you gravel clean the substrate when you do a water change?
Do you dechlorinate the new water before adding it to the tank?
Have you added any new fish or plants during the last 2 weeks?
Did you do anything to the tank yesterday or this morning before heading off to work?
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The best thing to do if a fish looks unwell is a 75% water change and gravel clean the substrate. Do this each day until the issue is identified or resolved. Wipe the inside of the glass down and clean the filter if it hasn't been done in the last 2 weeks.
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The most common issue with rainbowfish is protozoan infections caused by lack of big water changes, and a dirty environment. Doing a 75% water change and gravel cleaning the substrate each day for a week or more will usually help. If it doesn't you can add salt.
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, 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. Then do a 20% water change each day for a week. Then you can do bigger water changes after that.
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How often do you feed the fish?
Do you feed the fish any plant matter?
Rainbowfishes need plant matter in their diet. Duckweed (floating plant) is ideal for rainbowfish and grows rapidly indoors or outdoors in a plastic tub. Algae and other soft leaved plants can also be fed to them. If you use a dry food, feed them a goldfish flake and some algae/ spirulina flakes.
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The bent rainbow could have an internal infection. Was it skinny before? How well was it eating?
