What possible fish illness

I know asking about a possible illness without photo or video documentation is foolish, but maybe the description will be enough for someone to recognize.
In the past year that this tank was running with this fish, I have lost 3 or 4 fish in the same manner. Given that the fish were juvenile when purchased and should have a lifespan of 4 years it is hard to dismiss.
I am talking about my golden white cloud minnows (havent noticed it in the normal color ones). The fish will behave as if the tail section is heavy, it will drag it down and the fish in span of days/weeks will rest on the bottom of the tank. It will be able to swim and feed, but all movements are jerk like with the tail section droopping lower. There are no distortions, no bloat, no sunken belly, no poop indicators, no visible injuries, flukes or parasites and also no loss of color. For all intents and purposes the fish looks normal, but doesnt swim normal and will die at some point.

Could it be my feeding? I most definitely overfeed the minnows, because I am also trying to feed the garras and sewellias, but the minnows eat the biggest fill. I feed once every two days to have them fast in between. I feed mostly frozen (bbs,cyclops,daphnia,mosquito larvae,bloodworms no more than once a week), live bbs and microworms (also no more than once a week), sometimes algae wafer or repashy gel food and once a week some fort of flake food, be it fluval bug bites or tropical krill flakes. I will also feed some sort of vegetable every other week mainly for the sewellia but the minnows will literally eat anything. The temp is 20-21C° quite fast flow and I do a weekly water change of 30%.

Any suggestion is appreciated

Anytime there are issues in my tank, the first thing I do is a large water change...even if I just did one. 30% isn't really effective in such a large (and beautiful, TFF Tank of The Month contender hint, hint) aquarium. I would be doing 50% at the least, especially with the foods you're feeding. Have you tested the water?

Does the appearance of the fish deteriate at all just before they die? It would be really helpful if you could snap a photo the next time you spot a fish with any symptoms.

This has nothing to do with food.

It could be inbred fish that are genetically weak, or a disease (maybe protozoan). But need pictures and video of the fish swimming, eating and moving.

A big water change and gravel clean, as well as cleaning the filter is a start, especially if it's a protozoan infection. These are more common in tanks that get lots of food or have lots of fish in, and have dirty gravel and dirty filters.

I don't know how clean the tank is but big rocks and Java Moss can trap a lot of gunk that will breed protozoa.

Colin_T said:

I don't know how clean the tank is but big rocks and Java Moss can trap a lot of gunk that will breed protozoa.

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I removed half the rocks recently and every other water change I do I vacuum under the java moss very intensly to avoid the buildup. I also vacuum between the stones as well to try to keep it clean

once the issue occurs again I will document it better for sure so we know better next time. I always assume that if it were bacterial or something it would wipe more of the tank quicker, not just one fish once in a while. Granted I lost some sewellia in the past year as well

CaptainBarnicles said:

I would be doing 50% at the least, especially with the foods you're feeding. Have you tested the water?

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I dont test much, sometimes NO2 and NO3 and results were ok every time. I cant really do a 50% water change because I use cold water from a tap and it takes a long time to equalize temps since the tank has no heater. I can implement changes more frequently, but not higher volume.

If it was a bacterial infection it would kill a lot of fish at the time it appears. Bacterial infections generally cause the infected area to go red and sometimes inflamed.

Fungal infections in fish usually cause the damaged tissue to go white and fluffy. As a general rule, fungus will normally only enter damaged tissue (a wound or sore). However, there are some types of fungus that can infect healthy tissue too.

If it was some sort of external parasite you would see it crawling over the fish, so that can be ruled out.

Pretty much leaves us with a protozoan infection or poor genetics. A protozoan infection will normally show up as a cream, white or grey patch/ film over part or parts of the body. Depending on how badly infected the fish is, it might not produce anything more than a very thin pale cream film over a small section of the body, and this can be easy to miss on small fish.

Clean water, gravel and filter helps reduce the number of microscopic organisms in the water. Salt can be used to treat the three issues listed above.

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SALT
Using Salt to Treat Fish Health Issues.
For some fish diseases you can use salt (sodium chloride) to treat the ailment rather than using a chemical based medication. Salt is relatively safe and is regularly used in the aquaculture industry to treat food fish for diseases. Salt has been successfully used to treat minor fungal and bacterial infections, as well as a number of external protozoan infections. Salt alone will not treat whitespot (Ichthyophthirius) or Velvet (Oodinium) but will treat most other types of external protozoan infections in freshwater fishes. Salt can treat early stages of hole in the head disease caused by Hexamita but it needs to be done in conjunction with cleaning up the tank. Salt can also be used to treat anchor worm (Lernaea), fish lice (Argulus), gill flukes (Dactylogyrus), skin flukes (Gyrodactylus), Epistylis, Microsporidian and Spironucleus infections.

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 1 heaped tablespoon per 20 litres (5 gallons) 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.

Beastije said:

I dont test much, sometimes NO2 and NO3 and results were ok every time. I cant really do a 50% water change because I use cold water from a tap and it takes a long time to equalize temps since the tank has no heater. I can implement changes more frequently, but not higher volume.

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I've been using only outdoor tap water this winter so the water is too cold to use. I throw in a couple heaters with a powerhead into a bucket with new water and then boil some water on the stove, and throw that in, to up the temps. Has worked well.

I use cold tap water for water changes as I can't use hot tap water to warm it due to our water system. I boil a kettle of water to warm each bucketful of new water.

I will have to do something like that, but I put the water with hose in the tank itself, no extra step with a bucket. I just do it slowly and take about an hour or more to fill the tank back in, so the temp difference is not so drastic. Or I hope so.

I'm guessing it's internal. But I can't say what's inside.

I have seen it, or something very similar. The fish lists to the back, and generally settles like a shipwreck. At that point, it dies quickly. It's intermittent, and takes time. Here, it never spread to other species, but it always killed all the fish in the affected group. This could point to inbreeding (it is a linebred morph and large suppliers aren't as careful as show breeders), or it could point to a slow pathogen that was in the fish before you got them.

That was my conclusion when I saw it. As always with disease we can't see, it may be a coincidence.

Another one seems like it is affected
I took a video ( daylight, so glare), and am going to do a water change (was planned anyway)

The little skinny white cloud that keeps sinking to the bottom has a swim bladder problem. There's no cure for it and if it has happened to other white clouds, it is genetic. The fish should be euthanised because it is stressful for them not being able to swim normally or stay buoyant.

That is sad to hear. So far the gold line is affected, I bought almost all the stock from the same breeder, lost 4 fish to it, maybe 5 in the past year, they are over a year old. The normal line is not having this issue
How come it happens so sudden in a fish that previously didnt experience it? Just curious

Usually old age and poor genetics (inbreeding). These are small fish that only live to 4 or 5 years at most and that includes an extensive period of time in cold water (10-15C). If they are kept in tropical conditions (20C+) they age quicker and die sooner.

If you cross breed the gold with the normal, you will probably get healthier young that might not have this condition.

Can this decline be sped up by a cold water change? I always do a cold one on most of my tanks. On Thursday i was watching the tank closely, nothing. Today morning a slow water change, now i see another minnow (gold again) declining.