Bubblelike lump on guppy tail

[kropek88]

Hi everyone,
our 7 months old male guppy born in our aquarium (20 liters with only guppies) developed a bubble-like lump on its tale. It is active and with no damages on any scale. What could it be?

Thank you!

 

[Colin_T]

can you take some better pictures?

 

[kropek88]

Sure,
thank you for your answer!
Here the picture.

 

[Colin_T]

It could be a bacterial infection. There are occasional reports here with guppies developing lumps similar to those. There hasn't been any cure for them and the fish end up dying. However, you could try cleaning the tank and adding salt. Salt won't hurt the fish but might help.

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Wipe the inside of the glass with a clean fish sponge.

Clean the filter if it hasn't been done in the last 2 weeks. Wash filter media/ materials in a bucket of tank water and re-use them.

Do a 75% water change and gravel clean the substrate every day for a week.
Make sure any new water is free of chlorine/ chloramine before it's added to the tank.

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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 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, 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.

 

[kropek88]

Thank you so much!