Cloud minnow wasting away. What should I do?

[Aline19]

Hey guys, first time posting.
Caveat: I am not sure there is anything I can do to save the fish. Pet shop guy thinks it's a degenerative neurological condition, but I wonder what you think is going on.
Setup: 20 gal with fluval c4 hob plus sponge filter. Been running for 3 and a half years. Have some Java fern and moss.
I have 3 clouds (not counting the sick one currently in 3 gallon hospital), 6 pigmy cory, 2 nerites, a bunch of assassins (initially 4 to take care of pond snails,but they have been breeding a lot) for the past 3 and a half years. I also added 5 amano shrimps a few months back and 5 khuli loaches 5 months ago.
Weekly 20% water change plus filter maintenance every two weeks. Parameters are ammonia 0, nitrite 0, nitrates hovers between 5 and 10 ppm, although usually around 5. Ph 7.2 and phosphorus 0.5.
The one thing that changed recently (4 months ago) was that I added a heater (so went from 22 to 25 celsius) because I rescued 5 khuli loaches and after reading about them I figured they were more "fragile" than the clouds so I wanted to give them the best chance of survival and thought that the clouds would tolerate 25, although not super ideal.
Since then I lost 2 clouds (plus a third one not doing great right now). The two other clouds died from different things. One died overnight (was fine the day before so no idea what happened). The second started developing a big fluid filled lump under its eye over the course of a few months and eventually died (I tried salt and tetra medications). Now I have a third one that started wasting away 3 weeks ago. I first noticed that he was alway floating and had trouble swimming down. After a few days, I noticed a lesion on its back. At which point I moved him to a 3 gallon hospital. First tried salt for a few day. Helped with the lesion, but I could see that it would not save him. So I tried betta revive (that was the only medication I had on hand) for 3 days and saw no improvements. So I bought tetra medicine tabs and tried that for a few days but condition still progressed (spine is curving in like a S shape and he's alway swimming sideways in a weird bend... See pictures) although the lesions had healed. Gills seems red (could be too much salt? I stared at half a table spoon in 3 gallons increasing to 2 table spoon over a few days) and colors on the body are faded, although his fins a super nice and in perfect condition . Did not notice much improvement so reduced back to 1 TBS bc I was worried that 2 was too much.
So what do you think? Could this just be aging or a disease that could be cured? Should I put him out of his misery or is there something else I could try?
I mean he is a real warrior! Every morning a see him hanging at the top thinking he is dead, but no, his still alive and somehow still eating a bit and swimming around.
Ps sorry for the extra long post..
.

 

[Colin_T]

Hi and welcome to the forum

It could be old age and the fish are simply dying from age related ailments.

The first picture the fish appears to have a red blister growing out from its back. That is probably a cyst and there's no real cure for them apart from surgery and the fish usually die during the surgery. Euthanasia is the best thing for fish like that.

Fish that have bent are usually in pain and have internal problems (organ failure or a growth). If the fish bend slowly over months, then it's usually an internal growth. If they bend overnight, it's major internal organ failure. The fish should be euthanised if they bend.

The white body (muscle tissue under the skin) could be a microsporidian infection. Salt is the best treatment for this. See directions below.

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SALT
You can add rock salt (often sold as aquarium salt), swimming pool salt, or any non iodised salt (sodium chloride) 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, 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, 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.

 

[Aline19]

Thanks for your quick reply. In the first picture, the red thing is a food flake ��. But the fish did have a lesion on its back that healed. But yeah, its spine is becoming more and more crooked, like in a s shape, and it's been evolving for 3 weeks. I think I will put him out. But man I feel so bad for him. He has such a strong will to live. I can't believe he is still eating and swimming around. But if you think it's age related, that there is no cure and especially if he is suffering, I guess that is the only thing to do ��

 

[Colin_T]

If a fish can swim normally and still eat, then it's fine to try and keep them alive, but when they cant swim properly or start bending, then it's best to euthanise, even if the fish wants to live. They will struggle on for weeks or months and it becomes horrible watching them waste away. So I prefer to put them down when they can no longer swim properly or when they stop eating.