Dwarf Rasbora, very thin and pale

[P.erson]

Hi, I’m new to this website so sorry if formatting and stuff looks weird.
Anyway, one of my rasboras looks very thin and pale, seems to be hyperventilating, hides a lot and gasps for air at the surface when not hiding. I haven’t seen it eat a lot either.
Nitrate:0
Nitrite:0
TH: 7>14
KH carbonate Hardness: 10
pH: 7
Chlorine: 0
I changed half of the water this morning. It’s a 30L tank. The 7 rasboras share the tank with about 50+ fire/cherry shrimps.

I’ve added some photos, one with a healthy fish next to it. Does anyone know what’s up with the (left) fish?

 

[Colin_T]

It has a microsporidian infection (muscle wasting disease).

The only cure I have found is salt and lots of it but rasboras don't like salt so you can try salt or you can watch it die.

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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.

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 (4 heaped tablespoons per 20 litres) will affect some plants and some snails. The lower dose rate will not affect 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.

 

[P.erson]

It has a microsporidian infection (muscle wasting disease).

The only cure I have found is salt and lots of it but rasboras don't like salt so you can try salt or you can watch it die.

---------------
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.

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 (4 heaped tablespoons per 20 litres) will affect some plants and some snails. The lower dose rate will not affect 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.

Thank you so much for your reply! Super helpful!